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/** 1. 分类(2大类)
* 基本(值)类型
* Number: 任意的数字
* boolean: true/false
* undefined: undefined
* null: null
*
* 对象(引用类型)
* object 任意对象
* Function 一种特别的对象(可以执行)
* Array 一种特别的对象(数值下标 内部数据是有序的)
*
* 2 判断
* typeof
* 可以判断 undefined / 数值 / 字符串 / 布尔值 / function
* 不可以判断 null 与 object object 与 array
*
* instanceof
* 判断对象的具体类型 Object, Array与Function
*
* ===
* 可以判断 undefined null
*/
var a;
console.log(typeof a, typeof a === ‘undefined‘, a === undefined); // undefined true true
console.log(undefined === ‘undefined‘); // false
a = 4
console.log(typeof a === ‘number‘); // true
a = ‘Eric‘
console.log(typeof a === ‘string‘); // true
a = true
console.log(typeof a === ‘boolean‘); // true
a = null
console.log(typeof a, a === null); // ‘object‘ true
console.log(‘----------------------‘);
// 2 对象
var b1 = {
b2: [2, ‘abc‘, console.log],
b3: function () {
console.log(‘b3()‘)
return function(){
return ‘Eric‘
}
}
}
console.log(b1 instanceof Object, b1 instanceof Array); // true false
console.log(b1.b2 instanceof Array, b1.b2 instanceof Object); // true true
console.log(b1.b3 instanceof Function, b1.b3 instanceof Object); // true true
console.log(typeof b1.b2,‘---‘); // ‘object‘
console.log(typeof b1.b3,typeof b1.b3 === ‘function‘); // function true
console.log(typeof b1.b2[2] === ‘function‘); // true
b1.b2[2](4) // 4
console.log(b1.b3()()); // Eric
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