【jQuery源码】工具函数

              1
            //
            扩展工具函数
              2
            jQuery.extend({

              3
            //
             Unique for each copy of jQuery on the page
              4     expando: "jQuery" + ( version + Math.random() ).replace( /\D/g, "" ),
  5  6// Assume jQuery is ready without the ready module  7     isReady: true,
  8  9     error: function( msg ) {
 10thrownew Error( msg );
 11    },
 12 13     noop: function() {},
 14 15// See test/unit/core.js for details concerning isFunction. 16// Since version 1.3, DOM methods and functions like alert 17// aren‘t supported. They return false on IE (#2968). 18     isFunction: function( obj ) {
 19return jQuery.type(obj) === "function";
 20    },
 21 22//首先判断是否支持ES5中的isArray 23     isArray: Array.isArray || function( obj ) {
 24return jQuery.type(obj) === "array";
 25    },
 26 27//之前版本是obj && typeof obj === "object" && "setInterval" in obj; 28     isWindow: function( obj ) {
 29/* jshint eqeqeq: false */ 30//window对象是一个包含自己的对象 window.window....window === window; 31return obj != null && obj == obj.window;
 32    },
 33 34     isNumeric: function( obj ) {
 35// parseFloat NaNs numeric-cast false positives (null|true|false|"") 36// ...but misinterprets leading-number strings, particularly hex literals ("0x...") 37// subtraction forces infinities to NaN 38// adding 1 corrects loss of precision from parseFloat (#15100) 39//当不是数字时，(obj - parseFloat( obj ) + 1)为NaN，所以>=0也就为false 40return !jQuery.isArray( obj ) && (obj - parseFloat( obj ) + 1) >= 0;
 41    },
 42 43     isEmptyObject: function( obj ) {
 44var name;
 45for ( name in obj ) {
 46returnfalse;
 47        }
 48returntrue;
 49    },
 50 51// 检查obj是否是一个纯粹的对象（通过"{}" 或 "new Object"创建的对象） 52// console.info( $.isPlainObject( {} ) ); // true 53// console.info( $.isPlainObject( ‘‘ ) ); // false 54// console.info( $.isPlainObject( document.location ) ); // true 55// console.info( $.isPlainObject( document ) ); // false 56// console.info( $.isPlainObject( new Date() ) ); // false 57// console.info( $.isPlainObject( ) ); // false 58     isPlainObject: function( obj ) {
 59var key;
 60 61// Must be an Object. 62// Because of IE, we also have to check the presence of the constructor property. 63// Make sure that DOM nodes and window objects don‘t pass through, as well 64// 必须是一个对象 65// 因为在IE8中会抛出非法指针异常，必须检查constructor属性 66// DOM节点和window对象，返回false 67// obj不存在 或 非object类型 或 DOM节点 或 widnow对象，直接返回false 68// 测试以下三中可能的情况： 69// jQuery.type(obj) !== "object" 类型不是object，忽略 70// obj.nodeType 认为DOM节点不是纯对象 71// jQuery.isWindow( obj ) 认为window不是纯对象 72if ( !obj || jQuery.type(obj) !== "object" || obj.nodeType || jQuery.isWindow( obj ) ) {
 73returnfalse;
 74        }
 75 76try {
 77// Not own constructor property must be Object 78// 测试constructor属性 79// 具有构造函数constructor，却不是自身的属性（即通过prototype继承的） 80if ( obj.constructor &&
 81                 !hasOwn.call(obj, "constructor") &&
 82                 !hasOwn.call(obj.constructor.prototype, "isPrototypeOf") ) {
 83returnfalse;
 84            }
 85         } catch ( e ) {
 86// IE8,9 Will throw exceptions on certain host objects #9897 87returnfalse;
 88        }
 89 90// Support: IE<9 91// Handle iteration over inherited properties before own properties. 92if ( support.ownLast ) {
 93for ( key in obj ) {
 94return hasOwn.call( obj, key );
 95            }
 96        }
 97 98// Own properties are enumerated firstly, so to speed up, 99// if last one is own, then all properties are own.100for ( key in obj ) {}
101102return key === undefined || hasOwn.call( obj, key );
103    },
104105     type: function( obj ) {
106if ( obj == null ) {
107return obj + "";//转成字符串的一种方法108        }
109returntypeof obj === "object" || typeof obj === "function" ?
110             class2type[ toString.call(obj) ] || "object" :
111typeof obj;
112    },
113114// Evaluates a script in a global context115// Workarounds based on findings by Jim Driscoll116// http://weblogs.java.net/blog/driscoll/archive/2009/09/08/eval-javascript-global-context117     globalEval: function( data ) {
118if ( data && jQuery.trim( data ) ) {
119// We use execScript on Internet Explorer120// We use an anonymous function so that context is window121// rather than jQuery in Firefox122             ( window.execScript || function( data ) {
123                 window[ "eval" ].call( window, data );
124            } )( data );
125        }
126    },
127128// Convert dashed to camelCase; used by the css and data modules129// Microsoft forgot to hump their vendor prefix (#9572)130     camelCase: function( string ) {
131return string.replace( rmsPrefix, "ms-" ).replace( rdashAlpha, fcamelCase );
132    },
133134//判断节点名称是否相同135     nodeName: function( elem, name ) {
136return elem.nodeName && elem.nodeName.toLowerCase() === name.toLowerCase();
137    },
138139// args is for internal usage only140//遍历对象或数组141     each: function( obj, callback, args ) {
142var value,
143             i = 0,
144             length = obj.length,
145             isArray = isArraylike( obj );
146147//如果有参数148if ( args ) {
149if ( isArray ) {
150for ( ; i < length; i++ ) {
151                     value = callback.apply( obj[ i ], args );
152153if ( value === false ) {
154break;
155                    }
156                }
157             } else {
158for ( i in obj ) {
159                     value = callback.apply( obj[ i ], args );
160161if ( value === false ) {
162break;
163                    }
164                }
165            }
166167// A special, fast, case for the most common use of each168//没有参数args则调用，则调用call，上下文设置为当前遍历到的对象，参数设置为key/index和value169         } else {
170if ( isArray ) {
171for ( ; i < length; i++ ) {
172                     value = callback.call( obj[ i ], i, obj[ i ] );
173174if ( value === false ) {
175break;
176                    }
177                }
178             } else {
179for ( i in obj ) {
180                     value = callback.call( obj[ i ], i, obj[ i ] );
181182if ( value === false ) {
183break;
184                    }
185                }
186            }
187        }
188189return obj;
190    },
191192// Support: Android<4.1, IE<9193//利用正则去掉前后空格194     trim: function( text ) {
195return text == null ?
196             "" :
197             ( text + "" ).replace( rtrim, "" );
198    },
199200// results is for internal usage only201     makeArray: function( arr, results ) {
202var ret = results || [];
203204if ( arr != null ) {
205if ( isArraylike( Object(arr) ) ) {//伪数组206                jQuery.merge( ret,
207typeof arr === "string" ?
208                    [ arr ] : arr
209                );
210             } else {//不是数组也不是伪数组211                push.call( ret, arr );
212            }
213        }
214215return ret;
216    },
217218//在数组中搜索指定的值，并返回其索引值,i为查找的起始位置219     inArray: function( elem, arr, i ) {
220var len;
221222if ( arr ) {
223if ( indexOf ) {// 是否有本地化的Array.prototype.indexOf224return indexOf.call( arr, elem, i );
225            }
226227             len = arr.length;
228             i = i ? i < 0 ? Math.max( 0, len + i ) : i : 0;
229230for ( ; i < len; i++ ) {
231// Skip accessing in sparse arrays232//i in arr表示arr[i]存在233if ( i in arr && arr[ i ] === elem ) {
234return i;
235                }
236            }
237        }
238239return -1;
240    },
241242//将数组second合并到数组first中243     merge: function( first, second ) {
244var len = +second.length,
245             j = 0,
246             i = first.length;
247248while ( j < len ) {
249             first[ i++ ] = second[ j++ ];
250        }
251252// Support: IE<9253// Workaround casting of .length to NaN on otherwise arraylike objects (e.g., NodeLists)254//在IE9以前，类数组对象的length为NaN255if ( len !== len ) {
256while ( second[j] !== undefined ) {
257                 first[ i++ ] = second[ j++ ];
258            }
259        }
260261         first.length = i;
262263return first;
264    },
265266// 过滤数组，返回新数组；callback返回true时保留；如果inv为true，callback返回false才会保留267     grep: function( elems, callback, invert ) {
268var callbackInverse,
269             matches = [],
270             i = 0,
271             length = elems.length,
272             callbackExpect = !invert;
273274// Go through the array, only saving the items275// that pass the validator function276//遍历数组，将回调函数返回值push到结果数组277for ( ; i < length; i++ ) {
278             callbackInverse = !callback( elems[ i ], i );
279if ( callbackInverse !== callbackExpect ) {
280                matches.push( elems[ i ] );
281            }
282        }
283284return matches;
285    },
286287// arg is for internal usage only288//将数组或对象elems的元素/属性，转化成新的数组289     map: function( elems, callback, arg ) {
290var value,
291             i = 0,
292             length = elems.length,
293             isArray = isArraylike( elems ),
294             ret = [];
295296// Go through the array, translating each of the items to their new values297if ( isArray ) {//类数组或数组298for ( ; i < length; i++ ) {
299                 value = callback( elems[ i ], i, arg );
300301if ( value != null ) {
302                    ret.push( value );
303                }
304            }
305306// Go through every key on the object,307         } else {//对象308for ( i in elems ) {
309                 value = callback( elems[ i ], i, arg );
310311if ( value != null ) {
312                    ret.push( value );
313                }
314            }
315        }
316317// Flatten any nested arrays318// 使嵌套数组变平319// concat：320// 如果某一项为数组，那么添加其内容到末尾。321// 如果该项目不是数组，就将其作为单个的数组元素添加到数组的末尾。322return concat.apply( [], ret );
323    },
324325// A global GUID counter for objects326     guid: 1,
327328// Bind a function to a context, optionally partially applying any329// arguments.330// 代理方法：为fn指定上下文（即this）331     proxy: function( fn, context ) {
332var args, proxy, tmp;
333334//如果context是字符串格式，fn为fn[context]335//上下文环境设为fn336if ( typeof context === "string" ) {
337             tmp = fn[ context ];
338             context = fn;
339             fn = tmp;
340        }
341342// Quick check to determine if target is callable, in the spec343// this throws a TypeError, but we will just return undefined.344// 快速测试fn是否是可调用的（即函数）345// 但是这里仅返回undefined346if ( !jQuery.isFunction( fn ) ) {
347return undefined;
348        }
349350// Simulated bind351         args = slice.call( arguments, 2 );//从列表中去除前两个参数，即fn,context352         proxy = function() {
353return fn.apply( context || this, args.concat( slice.call( arguments ) ) );
354        };
355356// Set the guid of unique handler to the same of original handler, so it can be removed357         proxy.guid = fn.guid = fn.guid || jQuery.guid++;
358359return proxy;
360    },
361362     now: function() {
363return +( new Date() );
364    },
365366// jQuery.support is not used in Core but other projects attach their367// properties to it so it needs to exist.368    support: support
369 });