【JavaScript】Object.prototype.toString.call()进行类型判断

权声明：本文为博主原创文章，未经博主允许不得转载。

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1. op = Object.prototype,
2. ostring = op.toString,
3. ...
4. function isFunction(it) {
5. return ostring.call(it) === ‘[object Function]‘;
6. }
7. function isArray(it) {
8. return ostring.call(it) === ‘[object Array]‘;
9. }

最近在看requireJS的源码时，看到上面一段代码，很是好奇，为啥进行类型判断时使用Object.prototype.toString? 如果是我的话就直接用typeof得了，后来查阅了一些资料：

typeof

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1. 在使用 typeof 运算符时采用引用类型存储值会出现一个问题，无论引用的是什么类型的对象，它都返回 "object"。

ECMA 对Object.prototype.toString的解释

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1. Object.prototype.toString ( )
2. When the toString method is called, the following steps are taken:
3. If the this value is undefined, return "[object Undefined]".
4. If the this value is null, return "[object Null]".
5. Let O be the result of calling ToObject passing the this value as the argument.
6. Let class be the value of the [[Class]] internal property of O.
7. Return the String value that is the result of concatenating the three Strings "[object ", class, and "]".

http://www.ecma-international.org/ecma-262/5.1/#sec-15.2.4.2

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1. var oP = Object.prototype,
2. toString = oP.toString;
3. console.log(toString.call([123]));//[object Array]
4. console.log(toString.call(‘123‘));//[object String]
5. console.log(toString.call({a: ‘123‘}));//[object Object]
6. console.log(toString.call(/123/));//[object RegExp]
7. console.log(toString.call(123));//[object Number]
8. console.log(toString.call(undefined));//[object Undefined]
9. console.log(toString.call(null));//[object Null]
10. //....

  1 // 对Date的扩展，将 Date 转化为指定格式的String
  2 // 月(M)、日(d)、小时(H)、分(m)、秒(s)、季度(q) 可以用 1-2 个占位符，
  3 // 年(y)可以用 1-4 个占位符，毫秒(S)只能用 1 个占位符(是 1-3 位的数字)
  4 // 例子：
  5 // (new Date()).Format("yyyy-MM-dd hh:mm:ss.S") ==> 2006-07-02 08:09:04.423
  6 // (new Date()).Format("yyyy-M-d h:m:s.S")      ==> 2006-7-2 8:9:4.18
  7 Date.prototype.Format = function (fmt) {
  8     var o = {
  9         "M+": this.getMonth() + 1, //月份
 10         "d+": this.getDate(), //日
 11         "H+": this.getHours(), //小时 --------*********仅支持24小时制**************
 12         "m+": this.getMinutes(), //分
 13         "s+": this.getSeconds(), //秒
 14         "q+": Math.floor((this.getMonth() + 3) / 3), //季度
 15         "S": this.getMilliseconds() //毫秒
 16     };
 17     if (/(y+)/.test(fmt)) fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
 18     for (var k in o)
 19         if (new RegExp("(" + k + ")").test(fmt)) fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));
 20     return fmt;
 21 };
 22
 23 //将指定的毫秒数加到此实例的值上
 24 Date.prototype.addMilliseconds = function (value) {
 25     var millisecond = this.getMilliseconds();
 26     this.setMilliseconds(millisecond + value);
 27     return this;
 28 };
 29 //将指定的秒数加到此实例的值上
 30 Date.prototype.addSeconds = function (value) {
 31     var second = this.getSeconds();
 32     this.setSeconds(second + value);
 33     return this;
 34 };
 35 //将指定的分钟数加到此实例的值上
 36 Date.prototype.addMinutes = function (value) {
 37     var minute = this.addMinutes();
 38     this.setMinutes(minute + value);
 39     return this;
 40 };
 41 //将指定的小时数加到此实例的值上
 42 Date.prototype.addHours = function (value) {
 43     var hour = this.getHours();
 44     this.setHours(hour + value);
 45     return this;
 46 };
 47 //将指定的天数加到此实例的值上
 48 Date.prototype.addDays = function (value) {
 49     var date = this.getDate();
 50     this.setDate(date + value);
 51     return this;
 52 };
 53 //将指定的星期数加到此实例的值上
 54 Date.prototype.addWeeks = function (value) {
 55     return this.addDays(value * 7);
 56 };
 57 //将指定的月份数加到此实例的值上
 58 Date.prototype.addMonths = function (value) {
 59     var month = this.getMonth();
 60     this.setMonth(month + value);
 61     return this;
 62 };
 63 //将指定的年份数加到此实例的值上
 64 Date.prototype.addYears = function (value) {
 65     var year = this.getFullYear();
 66     this.setFullYear(year + value);
 67     return this;
 68 };
 69
 70
 71 /**
 72  * @ngdoc function
 73  * @name sUndefined
 74  * @module ng
 75  * @kind function
 76  *
 77  * @description
 78  * Determines if a reference is undefined.
 79  *
 80  * @param {*} value Reference to check.
 81  * @returns {boolean} True if `value` is undefined.
 82  */
 83 function isUndefined(value) { return typeof value === ‘undefined‘; }
 84
 85
 86 /**
 87  * @ngdoc function
 88  * @name sDefined
 89  * @module ng
 90  * @kind function
 91  *
 92  * @description
 93  * Determines if a reference is defined.
 94  *
 95  * @param {*} value Reference to check.
 96  * @returns {boolean} True if `value` is defined.
 97  */
 98 function isDefined(value) { return typeof value !== ‘undefined‘; }
 99
100
101 /**
102  * @ngdoc function
103  * @name sObject
104  * @module ng
105  * @kind function
106  *
107  * @description
108  * Determines if a reference is an `Object`. Unlike `typeof` in JavaScript, `null`s are not
109  * considered to be objects. Note that JavaScript arrays are objects.
110  *
111  * @param {*} value Reference to check.
112  * @returns {boolean} True if `value` is an `Object` but not `null`.
113  */
114 function isObject(value) {
115     // http://jsperf.com/isobject4
116     return value !== null && typeof value === ‘object‘;
117 }
118
119
120 /**
121  * Determine if a value is an object with a null prototype
122  *
123  * @returns {boolean} True if `value` is an `Object` with a null prototype
124  */
125 function isBlankObject(value) {
126     return value !== null && typeof value === ‘object‘ && !getPrototypeOf(value);
127 }
128
129
130 /**
131  * @ngdoc function
132  * @name sString
133  * @module ng
134  * @kind function
135  *
136  * @description
137  * Determines if a reference is a `String`.
138  *
139  * @param {*} value Reference to check.
140  * @returns {boolean} True if `value` is a `String`.
141  */
142 function isString(value) { return typeof value === ‘string‘; }
143
144
145 /**
146  * @ngdoc function
147  * @name sNumber
148  * @module ng
149  * @kind function
150  *
151  * @description
152  * Determines if a reference is a `Number`.
153  *
154  * This includes the "special" numbers `NaN`, `+Infinity` and `-Infinity`.
155  *
156  * If you wish to exclude these then you can use the native
157  * [`isFinite‘](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/isFinite)
158  * method.
159  *
160  * @param {*} value Reference to check.
161  * @returns {boolean} True if `value` is a `Number`.
162  */
163 function isNumber(value) { return typeof value === ‘number‘; }
164
165
166 /**
167  * @ngdoc function
168  * @name sDate
169  * @module ng
170  * @kind function
171  *
172  * @description
173  * Determines if a value is a date.
174  *
175  * @param {*} value Reference to check.
176  * @returns {boolean} True if `value` is a `Date`.
177  */
178 function isDate(value) {
179     return Object.prototype.toString.call(value) === ‘[object Date]‘;
180 }
181
182
183 /**
184  * @ngdoc function
185  * @name sArray
186  * @module ng
187  * @kind function
188  *
189  * @description
190  * Determines if a reference is an `Array`.
191  *
192  * @param {*} value Reference to check.
193  * @returns {boolean} True if `value` is an `Array`.
194  */
195
196
197 function isArray(value) {
198     return Object.prototype.toString.call(value) === ‘[object Array]‘;
199 }
200
201 /**
202  * @ngdoc function
203  * @name sFunction
204  * @module ng
205  * @kind function
206  *
207  * @description
208  * Determines if a reference is a `Function`.
209  *
210  * @param {*} value Reference to check.
211  * @returns {boolean} True if `value` is a `Function`.
212  */
213 function isFunction(value) { return typeof value === ‘function‘; }
214
215
216 /**
217  * Determines if a value is a regular expression object.
218  *
219  * @private
220  * @param {*} value Reference to check.
221  * @returns {boolean} True if `value` is a `RegExp`.
222  */
223 function isRegExp(value) {
224     return Object.prototype.toString.call(value) === ‘[object RegExp]‘;
225 }
226
227
228 /**
229  * Checks if `obj` is a window object.
230  *
231  * @private
232  * @param {*} obj Object to check
233  * @returns {boolean} True if `obj` is a window obj.
234  */
235 function isWindow(obj) {
236     return obj && obj.window === obj;
237 }
238
239
240 function isScope(obj) {
241     return obj && obj.$evalAsync && obj.$watch;
242 }
243
244
245 function isFile(obj) {
246     return Object.prototype.toString.call(obj) === ‘[object File]‘;
247 }
248
249
250 function isFormData(obj) {
251     return Object.prototype.toString.call(obj) === ‘[object FormData]‘;
252 }
253
254
255 function isBlob(obj) {
256     return Object.prototype.toString.call(obj) === ‘[object Blob]‘;
257 }
258
259
260 function isBoolean(value) {
261     return typeof value === ‘boolean‘;
262 }
263
264
265 function isNullOrEmpty(str) {
266     if (str && str.length > 0) {
267         return false;
268     }
269     return true;
270 }
271
272 function trim(str)
273 {
274     return str.replace(/(^\s*)|(\s*$)/g, ‘‘);
275 }
276
277
278 function ltrim(str)
279 {
280     return str.replace(/^\s*/g,‘‘);
281 }
282
283
284 function rtrim(str)
285 {
286     return str.replace(/\s*$/,‘‘);
287 }
288
289
290
291 function equals(str1, str2)
292 {
293     if(str1 == str2)
294     {
295         return true;
296     }
297     return false;
298 }
299
300
301 function equalsIgnoreCase(str1, str2)
302 {
303     if(str1.toUpperCase() == str2.toUpperCase())
304     {
305         return true;
306     }
307     return false;
308 }
309
310
311 function isChinese(str)
312 {
313     var str = str.replace(/(^\s*)|(\s*$)/g,‘‘);
314     if (!(/^[\u4E00-\uFA29]*$/.test(str)
315             && (!/^[\uE7C7-\uE7F3]*$/.test(str))))
316     {
317         return false;
318     }
319     return true;
320 }
321
322
323 function isEmail(str)
324 {
325     if(/^[\w-]+(\.[\w-]+)*@[\w-]+(\.[\w-]+)+$/.test(str))
326     {
327         return true
328     }
329     return false;
330 }
331
332
333 function isImg(str)
334 {
335     var objReg = new RegExp("[.]+(jpg|jpeg|swf|gif)$", "gi");
336     if(objReg.test(str))
337     {
338         return true;
339     }
340     return false;
341 }
342
343
344 function isInteger(str)
345 {
346     if(/^-?\d+$/.test(str))
347     {
348         return true;
349     }
350     return false;
351 }
352
353
354 function isFloat(str)
355 {
356     if(/^(-?\d+)(\.\d+)?$/.test(str))
357     {
358         return true;
359     }
360     return false;
361 }
362
363
364
365 function isMobile(str)
366 {
367     if(/^1[35]\d{9}/.test(str))
368     {
369         return true;
370     }
371     return false;
372 }
373
374
375 function isPhone(str)
376 {
377     if(/^(0[1-9]\d{1,2}-)\d{7,8}(-\d{1,8})?/.test(str))
378     {
379         return true;
380     }
381     return false;
382 }
383
384 function isIP(str){
385     var reg = /^(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9])\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9]|0)\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9]|0)\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[0-9])$/;
386     if(reg.test(str))
387     {
388         return true;
389     }
390     return false;
391 }
392
393
394 function isDateTimeString(str)
395 {
396     var reg = /^((((1[6-9]|[2-9]\d)\d{2})-(0?[13578]|1[02])-(0?[1-9]|[12]\d|3[01]))|(((1[6-9]|[2-9]\d)\d{2})-(0?[13456789]|1[012])-(0?[1-9]|[12]\d|30))|(((1[6-9]|[2-9]\d)\d{2})-0?2-(0?[1-9]|1\d|2[0-8]))|(((1[6-9]|[2-9]\d)(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00))-0?2-29-))$/;
397     if(reg.test(str))
398     {
399         return true;
400     }
401     return false;
402 }
403