ExtJs--15--Ext.is*各种类型判断的方法,简单看源码就可以明白了

/**
* Returns true if the passed value is empty, false otherwise. The value is deemed to be empty if it is either:
*
* - `null`
* - `undefined`
* - a zero-length array
* - a zero-length string (Unless the `allowEmptyString` parameter is set to `true`)
*
* @param {Object} value The value to test
* @param {Boolean} allowEmptyString (optional) true to allow empty strings (defaults to false)
* @return {Boolean}
* @markdown
*/
isEmpty: function(value, allowEmptyString) {
return (value === null) || (value === undefined) || (!allowEmptyString ? value === '' : false) || (Ext.isArray(value) && value.length === 0);
},

/**
* Returns true if the passed value is a JavaScript Array, false otherwise.
*
* @param {Object} target The target to test
* @return {Boolean}
* @method
*/
isArray: ('isArray' in Array) ? Array.isArray : function(value) {
return toString.call(value) === '[object Array]';
},

/**
* Returns true if the passed value is a JavaScript Date object, false otherwise.
* @param {Object} object The object to test
* @return {Boolean}
*/
isDate: function(value) {
return toString.call(value) === '[object Date]';
},

/**
* Returns true if the passed value is a JavaScript Object, false otherwise.
* @param {Object} value The value to test
* @return {Boolean}
* @method
*/
isObject: (toString.call(null) === '[object Object]') ?
function(value) {
// check ownerDocument here as well to exclude DOM nodes
return value !== null && value !== undefined && toString.call(value) === '[object Object]' && value.ownerDocument === undefined;
} :
function(value) {
return toString.call(value) === '[object Object]';
},

/**
* @private
*/
isSimpleObject: function(value) {
return value instanceof Object && value.constructor === Object;
},
/**
* Returns true if the passed value is a JavaScript 'primitive', a string, number or boolean.
* @param {Object} value The value to test
* @return {Boolean}
*/
isPrimitive: function(value) {
var type = typeof value;

return type === 'string' || type === 'number' || type === 'boolean';
},

/**
* Returns true if the passed value is a JavaScript Function, false otherwise.
* @param {Object} value The value to test
* @return {Boolean}
* @method
*/
isFunction:
// Safari 3.x and 4.x returns 'function' for typeof <NodeList>, hence we need to fall back to using
// Object.prototype.toString (slower)
(typeof document !== 'undefined' && typeof document.getElementsByTagName('body') === 'function') ? function(value) {
return toString.call(value) === '[object Function]';
} : function(value) {
return typeof value === 'function';
},

/**
* Returns true if the passed value is a number. Returns false for non-finite numbers.
* @param {Object} value The value to test
* @return {Boolean}
*/
isNumber: function(value) {
return typeof value === 'number' && isFinite(value);
},

/**
* Validates that a value is numeric.
* @param {Object} value Examples: 1, '1', '2.34'
* @return {Boolean} True if numeric, false otherwise
*/
isNumeric: function(value) {
return !isNaN(parseFloat(value)) && isFinite(value);
},

/**
* Returns true if the passed value is a string.
* @param {Object} value The value to test
* @return {Boolean}
*/
isString: function(value) {
return typeof value === 'string';
},

/**
* Returns true if the passed value is a boolean.
*
* @param {Object} value The value to test
* @return {Boolean}
*/
isBoolean: function(value) {
return typeof value === 'boolean';
},

/**
* Returns true if the passed value is an HTMLElement
* @param {Object} value The value to test
* @return {Boolean}
*/
isElement: function(value) {
return value ? value.nodeType === 1 : false;
},

/**
* Returns true if the passed value is a TextNode
* @param {Object} value The value to test
* @return {Boolean}
*/
isTextNode: function(value) {
return value ? value.nodeName === "#text" : false;
},

/**
* Returns true if the passed value is defined.
* @param {Object} value The value to test
* @return {Boolean}
*/
isDefined: function(value) {
return typeof value !== 'undefined';
},

/**
* Returns true if the passed value is iterable, false otherwise
* @param {Object} value The value to test
* @return {Boolean}
*/
isIterable: function(value) {
var type = typeof value,
checkLength = false;
if (value && type != 'string') {
// Functions have a length property, so we need to filter them out
if (type == 'function') {
// In Safari, NodeList/HTMLCollection both return "function" when using typeof, so we need
// to explicitly check them here.
if (Ext.isSafari) {
checkLength = value instanceof NodeList || value instanceof HTMLCollection;
}
} else {
checkLength = true;
}
}
return checkLength ? value.length !== undefined : false;
}