源地址https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/typeof
typeof操作符
1 // Numbers
2 typeof 37 === 'number';
3 typeof 3.14 === 'number';
4 typeof Math.LN2 === 'number';
5 typeof Infinity === 'number';
6 typeof NaN === 'number'; // 尽管NaN是"Not-A-Number"的缩写
7 typeof Number(1) === 'number'; // 但不要使用这种形式!
8
9 // Strings
10 typeof "" === 'string';
11 typeof "bla" === 'string';
12 typeof (typeof 1) === 'string'; // typeof总是返回一个字符串
13 typeof String("abc") === 'string'; // 但不要使用这种形式!
14
15 // Booleans
16 typeof true === 'boolean';
17 typeof false === 'boolean';
18 typeof Boolean(true) === 'boolean'; // 但不要使用这种形式!
19
20 // Symbols
21 typeof Symbol() === 'symbol';
22 typeof Symbol('foo') === 'symbol';
23 typeof Symbol.iterator === 'symbol';
24
25 // Undefined
26 typeof undefined === 'undefined';
27 typeof declaredButUndefinedVariable === 'undefined';
28 typeof undeclaredVariable === 'undefined';
29
30 // Objects
31 typeof {a:1} === 'object';
32
33 // 使用Array.isArray 或者 Object.prototype.toString.call
34 // 区分数组,普通对象
35 typeof [1, 2, 4] === 'object';
36
37 typeof new Date() === 'object';
Array.isArray()判断是否为数组
1 var ar = [];
2 var result = Array.isArray(ar);
3 // Output: true
4
5 var ar = new Array();
6 var result = Array.isArray(ar);
7 // Output: true
8
9 var ar = [1, 2, 3];
10 var result = Array.isArray(ar);
11 // Output: true
12
13 var result = Array.isArray("an array");
14 document.write(result);
15 // Output: false
Object.prototype.toString.call()精准判断数据类型
1 console.log(Object.prototype.toString.call(123)) //[object Number]
2 console.log(Object.prototype.toString.call('123')) //[object String]
3 console.log(Object.prototype.toString.call(undefined)) //[object Undefined]
4 console.log(Object.prototype.toString.call(true)) //[object Boolean]
5 console.log(Object.prototype.toString.call({})) //[object Object]
6 console.log(Object.prototype.toString.call([])) //[object Array]
7 console.log(Object.prototype.toString.call(function(){})) //[object Function]