Ext.form.TextAreaクラス

Specify false to validate that the value's length is > 0 (defaults to true)

Note: this config is only used when this Component is rendered by a Container which has been configured to use an
AnchorLayout based layout manager, for example:

See Ext.layout.AnchorLayout.anchor also.

Specify the id of the element, a DOM element or an existing Element corresponding to a DIV that is already present in the document that specifies some structural markup for this component.

{
    xtype: 'box',
    autoEl: {
        tag: 'img',
        src: 'http://www.example.com/example.jpg'
    }
}, {
    xtype: 'box',
    autoEl: {
        tag: 'blockquote',
        html: 'autoEl is cool!'
    }
}, {
    xtype: 'container',
    autoEl: 'ul',
    cls: 'ux-unordered-list',
    items: {
        xtype: 'box',
        autoEl: 'li',
        html: 'First list item'
    }
}

A tag name or
DomHelper spec used to create the Element which will encapsulate this Component.

You do not normally need to specify this. For the base classes Ext.Component, Ext.BoxComponent, and Ext.Container, this defaults to 'div'. The more complex Ext classes use a more complex DOM structure created by their own onRender methods.

This is intended to allow the developer to create application-specific utility Components encapsulated by different DOM elements. Example usage:

{
    xtype: 'box',
    autoEl: {
        tag: 'img',
        src: 'http://www.example.com/example.jpg'
    }
}, {
    xtype: 'box',
    autoEl: {
        tag: 'blockquote',
        html: 'autoEl is cool!'
    }
}, {
    xtype: 'container',
    autoEl: 'ul',
    cls: 'ux-unordered-list',
    items: {
        xtype: 'box',
        autoEl: 'li',
        html: 'First list item'
    }
}

var w = new Ext.Window({
    title: 'Window',
    width: 600,
    autoHeight: true,
    items: {
        title: 'Collapse Me',
        height: 400,
        collapsible: true,
        border: false,
        listeners: {
            beforecollapse: function() {
                w.el.shadow.hide();
            },
            beforeexpand: function() {
                w.el.shadow.hide();
            },
            collapse: function() {
                w.syncShadow();
            },
            expand: function() {
                w.syncShadow();
            }
        }
    }
}).show();

True to use height:'auto', false to use fixed height (or allow it to be managed by its parent
Container's layout manager. Defaults to false.

Note: Although many components inherit this config option, not all will function as expected with a height of 'auto'. Setting autoHeight:true means that the browser will manage height based on the element's contents, and that Ext will not manage it at all.

If the browser is managing the height, be aware that resizes performed by the browser in response to changes within the structure of the Component cannot be detected. Therefore changes to the height might result in elements needing to be synchronized with the new height. Example:

var w = new Ext.Window({
    title: 'Window',
    width: 600,
    autoHeight: true,
    items: {
        title: 'Collapse Me',
        height: 400,
        collapsible: true,
        border: false,
        listeners: {
            beforecollapse: function() {
                w.el.shadow.hide();
            },
            beforeexpand: function() {
                w.el.shadow.hide();
            },
            collapse: function() {
                w.syncShadow();
            },
            expand: function() {
                w.syncShadow();
            }
        }
    }
}).show();

True if the component should check for hidden classes (e.g. 'x-hidden' or 'x-hide-display') and remove them on render (defaults to false).

<div id='grid-container' style='margin-left:25%;width:50%'></div>

var myPanel = new Ext.Panel({
    renderTo: 'grid-container',
    monitorResize: true, // ブラウザのリサイズをリレー
    title: 'Panel',
    height: 400,
    autoWidth: true,
    layout: 'hbox',
    layoutConfig: {
        align: 'stretch'
    },
    defaults: {
        flex: 1
    },
    items: [{
        title: 'Box 1',
    }, {
        title: 'Box 2'
    }, {
        title: 'Box 3'
    }],
});

True to use width:'auto', false to use fixed width (or allow it to be managed by its parent
Container's layout manager. Defaults to false.

Note: Although many components inherit this config option, not all will function as expected with a width of 'auto'. Setting autoWidth:true means that the browser will manage width based on the element's contents, and that Ext will not manage it at all.

If the browser is managing the width, be aware that resizes performed by the browser in response to changes within the structure of the Component cannot be detected. Therefore changes to the width might result in elements needing to be synchronized with the new width. For example, where the target element is:

<div id='grid-container' style='margin-left:25%;width:50%'></div>

A Panel rendered into that target element must listen for browser window resize in order to relay its child items when the browser changes its width:

var myPanel = new Ext.Panel({
    renderTo: 'grid-container',
    monitorResize: true, // relay on browser resize
    title: 'Panel',
    height: 400,
    autoWidth: true,
    layout: 'hbox',
    layoutConfig: {
        align: 'stretch'
    },
    defaults: {
        flex: 1
    },
    items: [{
        title: 'Box 1',
    }, {
        title: 'Box 2'
    }, {
        title: 'Box 3'
    }],
});

The CSS class used to to apply to the special clearing div rendered directly after each form field wrapper to provide field clearing (defaults to 'x-form-clear-left').

Note: this config is only used when this Component is rendered by a Container which has been configured to use the FormLayout layout manager (e.g. Ext.form.FormPanel or specifying layout:'form') and either a fieldLabel is specified or isFormField=true is specified.

See Ext.layout.FormLayout.fieldTpl also.

ctCls: 'x-box-layout-ct custom-class'

An optional extra CSS class that will be added to this component's container. This can be useful for adding customized styles to the container or any of its children using standard CSS rules. See Ext.layout.ContainerLayout.extraCls also.

Note: ctCls defaults to '' except for the following class which assigns a value by default:

To configure the above Class with an extra CSS class append to the default. For example, for BoxLayout (Hbox and Vbox):

ctCls: 'x-box-layout-ct custom-class'

True to disable the field (defaults to false).

Be aware that conformant with the HTML specification, disabled Fields will not be submitted.

The CSS class to apply to an empty field to style the
emptyText (defaults to 'x-form-empty-field'). This class is automatically added and removed as needed depending on the current field value.

The default text to place into an empty field (defaults to null).
Note: that this value will be submitted to the server if this field is enabled and configured with a name.

new Ext.FormPanel({
    height: 100,
    renderTo: Ext.getBody(),
    items: [{
        xtype: 'textfield',
        fieldLabel: 'Name'
    }]
});

The label text to display next to this Component (defaults to '').

Note: this config is only used when this Component is rendered by a Container which has been configured to use the FormLayout layout manager (e.g. Ext.form.FormPanel or specifying layout:'form').

Also see hideLabel and Ext.layout.FormLayout.fieldTpl.

Example use:

new Ext.FormPanel({
    height: 100,
    renderTo: Ext.getBody(),
    items: [{
        xtype: 'textfield',
        fieldLabel: 'Name'
    }]
});

The height of this component in pixels (defaults to auto). Note to express this dimension as a percentage or offset see Ext.Component.anchor.

new Ext.FormPanel({
    height: 100,
    renderTo: Ext.getBody(),
    items: [{
        xtype: 'textfield'
        hideLabel: true
    }]
});

true to completely hide the label element
(label and separator). Defaults to false. By default, even if you do not specify a fieldLabel the space will still be reserved so that the field will line up with other fields that do have labels. Setting this to true will cause the field to not reserve that space.

Note: see the note for clearCls.

Example use:

new Ext.FormPanel({
    height: 100,
    renderTo: Ext.getBody(),
    items: [{
        xtype: 'textfield'
        hideLabel: true
    }]
});

How this component should be hidden. Supported values are 'visibility' (css visibility), 'offsets' (negative offset position) and 'display' (css display).

Note: the default of 'display' is generally preferred since items are automatically laid out when they are first shown (no sizing is done while hidden).

True to hide and show the component's container when hide/show is called on the component, false to hide and show the component itself (defaults to false). For example, this can be used as a shortcut for a hide button on a window by setting hide:true on the button when adding it to its parent container.

The unique id of this component
(defaults to an auto-assigned id). You should assign an id if you need to be able to access the component later and you do not have an object reference available (e.g., using Ext.getCmp).

Note that this id will also be used as the element id for the containing HTML element that is rendered to the page for this component. This allows you to write id-based CSS rules to style the specific instance of this component uniquely, and also to select sub-elements using this component's id as the parent.

Note: to avoid complications imposed by a unique id also see itemId and ref.

Note: to access the container of an item see ownerCt.

The type attribute for input fields -- e.g. radio, text, password,
file (defaults to "text"). The types "file" and "password" must be used to render those field types currently -- there are no separate Ext components for those. Note that if you use inputType:'file', emptyText is not supported and should be avoided.

// フィールドのラベルにスタイルを適用:
<style>
    .required .x-form-item-label {font-weight:bold;color:red;}
</style>

new Ext.FormPanel({
    height: 100,
    renderTo: Ext.getBody(),
    items: [{
        xtype: 'textfield',
        fieldLabel: 'Name',
        itemCls: 'required' //このラベルにスタイルが適用されます

    },{
        xtype: 'textfield',
        fieldLabel: 'Favorite Color'
    }]
});

Note: this config is only used when this Component is rendered by a Container which has been configured to use the
FormLayout layout manager (e.g. Ext.form.FormPanel or specifying layout:'form').

An additional CSS class to apply to the div wrapping the form item element of this field. If supplied, itemCls at the field level will override the default itemCls supplied at the container level. The value specified for itemCls will be added to the default class ('x-form-item').

Since it is applied to the item wrapper (see Ext.layout.FormLayout.fieldTpl), it allows you to write standard CSS rules that can apply to the field, the label (if specified), or any other element within the markup for the field.

Note: see the note for fieldLabel.

Example use:

// Apply a style to the field's label:
<style>
    .required .x-form-item-label {font-weight:bold;color:red;}
</style>

new Ext.FormPanel({
    height: 100,
    renderTo: Ext.getBody(),
    items: [{
        xtype: 'textfield',
        fieldLabel: 'Name',
        itemCls: 'required' //this label will be styled

    },{
        xtype: 'textfield',
        fieldLabel: 'Favorite Color'
    }]
});

var c = new Ext.Panel({ //
    height: 300,
    renderTo: document.body,
    layout: 'auto',
    items: [
        {
            itemId: 'p1',
            title: 'Panel 1',
            height: 150
        },
        {
            itemId: 'p2',
            title: 'Panel 2',
            height: 150
        }
    ]
})
p1 = c.getComponent('p1'); // Ext.getCmp()と同じではない
p2 = p1.ownerCt.getComponent('p2'); // 兄弟を経由して参照

An itemId can be used as an alternative way to get a reference to a component when no object reference is available.
Instead of using an id with Ext.getCmp, use itemId with Ext.Container.getComponent which will retrieve itemId's or id's. Since itemId's are an index to the container's internal MixedCollection, the itemId is scoped locally to the container -- avoiding potential conflicts with Ext.ComponentMgr which requires a unique id.

var c = new Ext.Panel({ //
    height: 300,
    renderTo: document.body,
    layout: 'auto',
    items: [
        {
            itemId: 'p1',
            title: 'Panel 1',
            height: 150
        },
        {
            itemId: 'p2',
            title: 'Panel 2',
            height: 150
        }
    ]
})
p1 = c.getComponent('p1'); // not the same as Ext.getCmp()
p2 = p1.ownerCt.getComponent('p2'); // reference via a sibling

Also see id and ref.

Note: to access the container of an item see ownerCt.

new Ext.FormPanel({
    height: 100,
    renderTo: Ext.getBody(),
    layoutConfig: {
        labelSeparator: '~'   // レイアウトの設定は低い優先順位です (初期値 ':')

    },
    labelSeparator: '>>',     // コンテナレベルの設定
    items: [{
        xtype: 'textfield',
        fieldLabel: 'Field 1',
        labelSeparator: '...' // フィールド / コンポーネントレベルが他のものに取って代わります

    },{
        xtype: 'textfield',
        fieldLabel: 'Field 2' // ラベルセパレータは'='になるでしょう
    }]
});

The separator to display after the text of each
fieldLabel. This property may be configured at various levels. The order of precedence is:

To display no separator for this field's label specify empty string ''.

Note: see the note for clearCls.

Also see hideLabel and Ext.layout.FormLayout.fieldTpl.

Example use:

new Ext.FormPanel({
    height: 100,
    renderTo: Ext.getBody(),
    layoutConfig: {
        labelSeparator: '~'   // layout config has lowest priority (defaults to ':')

    },
    labelSeparator: '>>',     // config at container level
    items: [{
        xtype: 'textfield',
        fieldLabel: 'Field 1',
        labelSeparator: '...' // field/component level config supersedes others

    },{
        xtype: 'textfield',
        fieldLabel: 'Field 2' // labelSeparator will be '='
    }]
});

new Ext.FormPanel({
    height: 100,
    renderTo: Ext.getBody(),
    items: [{
        xtype: 'textfield',
        fieldLabel: 'Name',
        labelStyle: 'font-weight:bold;'
    }]
});

A CSS style specification string to apply directly to this field's label. Defaults to the container's labelStyle value if set
(e.g., Ext.layout.FormLayout.labelStyle , or '').

Note: see the note for clearCls.

Also see hideLabel and Ext.layout.FormLayout.fieldTpl.

Example use:

new Ext.FormPanel({
    height: 100,
    renderTo: Ext.getBody(),
    items: [{
        xtype: 'textfield',
        fieldLabel: 'Name',
        labelStyle: 'font-weight:bold;'
    }]
});

// Plugin is configured with a listeners config object.
// The Component is appended to the argument list of all handler functions.
Ext.DomObserver = Ext.extend(Object, {
    constructor: function(config) {
        this.listeners = config.listeners ? config.listeners : config;
    },

    // Component passes itself into plugin's init method
    init: function(c) {
        var p, l = this.listeners;
        for (p in l) {
            if (Ext.isFunction(l[p])) {
                l[p] = this.createHandler(l[p], c);
            } else {
                l[p].fn = this.createHandler(l[p].fn, c);
            }
        }

        // Add the listeners to the Element immediately following the render call
        c.render = c.render.createSequence(function() {
            var e = c.getEl();
            if (e) {
                e.on(l);
            }
        });
    },

    createHandler: function(fn, c) {
        return function(e) {
            fn.call(this, e, c);
        };
    }
});

var combo = new Ext.form.ComboBox({

    // Collapse combo when its element is clicked on
    plugins: [ new Ext.DomObserver({
        click: function(evt, comp) {
            comp.collapse();
        }
    })],
    store: myStore,
    typeAhead: true,
    mode: 'local',
    triggerAction: 'all'

});

A config object containing one or more event handlers to be added to this object during initialization.
This should be a valid listeners config object as specified in the addListener example for attaching multiple handlers at once.

DOM events from ExtJs Components

While some ExtJs Component classes export selected DOM events (e.g. "click", "mouseover" etc), this is usually only done when extra value can be added. For example the DataView's click event passing the node clicked on. To access DOM events directly from a Component's HTMLElement, listeners must be added to the Element after the Component has been rendered. A plugin can simplify this step:

// Plugin is configured with a listeners config object.
// The Component is appended to the argument list of all handler functions.
Ext.DomObserver = Ext.extend(Object, {
    constructor: function(config) {
        this.listeners = config.listeners ? config.listeners : config;
    },

    // Component passes itself into plugin's init method
    init: function(c) {
        var p, l = this.listeners;
        for (p in l) {
            if (Ext.isFunction(l[p])) {
                l[p] = this.createHandler(l[p], c);
            } else {
                l[p].fn = this.createHandler(l[p].fn, c);
            }
        }

        // Add the listeners to the Element immediately following the render call
        c.render = c.render.createSequence(function() {
            var e = c.getEl();
            if (e) {
                e.on(l);
            }
        });
    },

    createHandler: function(fn, c) {
        return function(e) {
            fn.call(this, e, c);
        };
    }
});

var combo = new Ext.form.ComboBox({

    // Collapse combo when its element is clicked on
    plugins: [ new Ext.DomObserver({
        click: function(evt, comp) {
            comp.collapse();
        }
    })],
    store: myStore,
    typeAhead: true,
    mode: 'local',
    triggerAction: 'all'

});

{
    top: (top margin),
    right: (right margin),
    bottom: (bottom margin),
    left: (left margin)
}

{top:0, right:0, bottom:0, left:0}

メモ: this config is only used when this BoxComponent is rendered by a Container which has been configured to use the BorderLayout or one of the two BoxLayout subclasses.

An object containing margins to apply to this BoxComponent in the format:

{
    top: (top margin),
    right: (right margin),
    bottom: (bottom margin),
    left: (left margin)
}

May also be a string containing space-separated, numeric margin values. The order of the sides associated with each value matches the way CSS processes margin values:

Defaults to:

{top:0, right:0, bottom:0, left:0}

var myField = new Ext.form.NumberField({
    id: 'mobile',
    anchor:'90%',
    fieldLabel: 'Mobile',
    maxLength: 16, // これは入力チェックのため
    autoCreate: {tag: 'input', type: 'text', size: '20', autocomplete: 'off', maxlength: '10'}
});

Maximum input field length allowed by validation (defaults to Number.MAX_VALUE).
This behavior is intended to provide instant feedback to the user by improving usability to allow pasting and editing or overtyping and back tracking.
To restrict the maximum number of characters that can be entered into the field use autoCreate to add any attributes you want to a field, for example:

var myField = new Ext.form.NumberField({
    id: 'mobile',
    anchor:'90%',
    fieldLabel: 'Mobile',
    maxLength: 16, // for validation
    autoCreate: {tag: 'input', type: 'text', size: '20', autocomplete: 'off', maxlength: '10'}
});

Error text to display if the
maximum length validation fails (defaults to 'The maximum length for this field is {maxLength}')

Error text to display if the
minimum length validation fails (defaults to 'The minimum length for this field is {minLength}')

Value         Description
-----------   ----------------------------------------------------------------------
qtip          ユーザがフィールド上でhoverする場合、quick tipを表示します。
title         ブラウザデフォルトのtitle属性のポップアップを表示します。
under         エラーテキストを含んでいるフィールドの下にdivブロックを追加します。
side          hoverしているポップアップのフィールドの右にエラーアイコンを追加します
[element id]  指定されたエレメントのinnerHTMLにエラーテキストを直接書き込みます。

The location where error text should display.
Should be one of the following values (defaults to 'qtip'):

Value         Description
-----------   ----------------------------------------------------------------------
qtip          Display a quick tip when the user hovers over the field
title         Display a default browser title attribute popup
under         Add a block div beneath the field containing the error text
side          Add an error icon to the right of the field with a popup on hover
[element id]  Add the error text directly to the innerHTML of the specified element

The field's HTML name attribute (defaults to "").
Note: this property must be set if this field is to be automatically included with form submit().

An optional extra CSS class that will be added to this component's Element when the mouse moves over the Element, and removed when the mouse moves out. (defaults to ''). This can be useful for adding customized 'active' or 'hover' styles to the component or any of its children using standard CSS rules.

An object or array of objects that will provide custom functionality for this component. The only requirement for a valid plugin is that it contain an init method that accepts a reference of type Ext.Component. When a component is created, if any plugins are available, the component will call the init method on each plugin, passing a reference to itself. Each plugin can then call methods or respond to events on the component as needed to provide its functionality.

The registered ptype to create. This config option is not used when passing a config object into a constructor. This config option is used only when lazy instantiation is being used, and a Plugin is being specified not as a fully instantiated Component, but as a Component config object. The ptype will be looked up at render time up to determine what type of Plugin to create.

If you create your own Plugins, you may register them using Ext.ComponentMgr.registerPlugin in order to be able to take advantage of lazy instantiation and rendering.

true to mark the field as readOnly in HTML(defaults to false).

Note: this only sets the element's readOnly DOM attribute. Setting readOnly=true, for example, will not disable triggering a ComboBox or DateField; it gives you the option of forcing the user to choose via the trigger without typing in the text box. To hide the trigger use hideTrigger.

var myGrid = new Ext.grid.EditorGridPanel({
    title: 'My EditorGridPanel',
    store: myStore,
    colModel: myColModel,
    tbar: [{
        text: 'Save',
        handler: saveChanges,
        disabled: true,
        ref: '../saveButton'
    }],
    listeners: {
        afteredit: function() {
//          The button reference is in the GridPanel
            myGrid.saveButton.enable();
        }
    }
});

A path specification, relative to the Component's
ownerCt specifying into which ancestor Container to place a named reference to this Component.

The ancestor axis can be traversed by using '/' characters in the path. For example, to put a reference to a Toolbar Button into the Panel which owns the Toolbar:

var myGrid = new Ext.grid.EditorGridPanel({
    title: 'My EditorGridPanel',
    store: myStore,
    colModel: myColModel,
    tbar: [{
        text: 'Save',
        handler: saveChanges,
        disabled: true,
        ref: '../saveButton'
    }],
    listeners: {
        afteredit: function() {
//          The button reference is in the GridPanel
            myGrid.saveButton.enable();
        }
    }
});

In the code above, if the ref had been 'saveButton' the reference would have been placed into the Toolbar. Each '/' in the ref moves up one level from the Component's ownerCt.

A JavaScript RegExp object to be tested against the field value during validation (defaults to null).
If the test fails, the field will be marked invalid using regexText.

The error text to display if
regex is used and the test fails during validation (defaults to '')

Note: this config is only used when this BoxComponent is rendered
by a Container which has been configured to use the BorderLayout layout manager (e.g. specifying layout:'border').

See Ext.layout.BorderLayout also.

Specify the id of the element,
a DOM element or an existing Element that this component will be rendered into.

See render also.

An array of events that, when fired, should trigger this component to save its state (defaults to none). stateEvents may be any type of event supported by this component, including browser or custom events (e.g., ['click', 'customerchange']).

See stateful for an explanation of saving and restoring Component state.

The unique id for this component to use for state management purposes (defaults to the component id if one was set, otherwise null if the component is using a generated id).
See stateful for an explanation of saving and restoring Component state.

Ext.state.Manager.setProvider(new Ext.state.CookieProvider({
    expires: new Date(new Date().getTime()+(1000*60*60*24*7)), //7 days from now
}));

A flag which causes the Component to attempt to restore the state of internal properties from a saved state on startup. The component must have either a stateId or id assigned for state to be managed. Auto-generated ids are not guaranteed to be stable across page loads and cannot be relied upon to save and restore the same state for a component.

For state saving to work, the state manager's provider must have been set to an implementation of Ext.state.Provider which overrides the set and get methods to save and recall name/value pairs. A built-in implementation, Ext.state.CookieProvider is available.

To set the state provider for the current page:

Ext.state.Manager.setProvider(new Ext.state.CookieProvider({
    expires: new Date(new Date().getTime()+(1000*60*60*24*7)), //7 days from now
}));

A stateful Component attempts to save state when one of the events listed in the stateEvents configuration fires.

To save state, a stateful Component first serializes its state by calling getState. By default, this function does nothing. The developer must provide an implementation which returns an object hash which represents the Component's restorable state.

The value yielded by getState is passed to Ext.state.Manager.set which uses the configured Ext.state.Provider to save the object keyed by the Component's stateId, or, if that is not specified, its id.

During construction, a stateful Component attempts to restore its state by calling Ext.state.Manager.get passing the stateId, or, if that is not specified, the id.

The resulting object is passed to applyState. The default implementation of applyState simply copies properties into the object, but a developer may override this to support more behaviour.

You can perform extra processing on state save and restore by attaching handlers to the beforestaterestore, staterestore, beforestatesave and statesave events.

new Ext.Panel({
    title: 'Some Title',
    renderTo: Ext.getBody(),
    width: 400, height: 300,
    layout: 'form',
    items: [{
        xtype: 'textarea',
        style: {
            width: '95%',
            marginBottom: '10px'
        }
    },
        new Ext.Button({
            text: 'Send',
            minWidth: '100',
            style: {
                marginBottom: '10px'
            }
        })
    ]
});

A custom style specification to be applied to this component's Element. Should be a valid argument to
Ext.Element.applyStyles.

new Ext.Panel({
    title: 'Some Title',
    renderTo: Ext.getBody(),
    width: 400, height: 300,
    layout: 'form',
    items: [{
        xtype: 'textarea',
        style: {
            width: '95%',
            marginBottom: '10px'
        }
    },
        new Ext.Button({
            text: 'Send',
            minWidth: '100',
            style: {
                marginBottom: '10px'
            }
        })
    ]
});

The tabIndex for this field. Note this only applies to fields that are rendered, not those which are built via applyTo (defaults to undefined).

A custom validation function to be called during field validation
(validateValue) (defaults to null). If specified, this function will be called first, allowing the developer to override the default validation process.

This function will be passed the following Parameters:

This function is to Return:

A custom error message to display in place of the default message provided
for the vtype currently set for this field (defaults to ''). Note: only applies if vtype is set, else ignored.

The width of this component in pixels (defaults to auto).
Note to express this dimension as a percentage or offset see Ext.Component.anchor.

The registered xtype to create. This config option is not used when passing a config object into a constructor. This config option is used only when lazy instantiation is being used, and a child item of a Container is being specified not as a fully instantiated Component, but as a Component config object. The xtype will be looked up at render time up to determine what type of child Component to create.

The predefined xtypes are listed here.

If you subclass Components to create your own Components, you may register them using Ext.ComponentMgr.registerType in order to be able to take advantage of lazy instantiation and rendering.