[js]Object.defineProperty等几个js特殊方法

Object.defineProperty

var obj = {
    test: "hello"
};

obj['favor'] = 'orange';
//对象已有的属性添加特性描述
// Object.defineProperty(obj, "test", {
//     configurable: true,
//     enumerable: true,
//     writable: true
// });
//对象新添加的属性的特性描述
Object.defineProperty(obj, "age", {
    configurable: true,
    value: 22,
    enumerable: true,
    writable: false
});

obj['age'] = 10;
console.log(obj);

检测类型Object.prototype.toString.call

Object.prototype.toString.call();

Object.prototype.toString.call([]); //"[object Array]"
Object.prototype.toString.call({}); //"[object Object]"
Object.prototype.toString.call(null); //"[object Null]"
Object.prototype.toString.call(undefined); //"[object Undefined]"

转数组

Array.prototype.slice().call(likeArr);

let likeArrToArr = function (likeArr) {
    var arr = [];
    try {
        arr = Array.prototype.slice.call(likeArr);
    } catch (e) {
        for (var i = 0; i < likeArr.length; i++) {
            arr[arr.length] = likeArr[i];
        }
    }

    return arr;
};

var arr = {length: 2, 0: 'first', 1: 'second'};
console.log(likeArrToArr(arr));

var arr2 = [0,11,22,33];
console.log(likeArrToArr(arr2));