开发中常用的JS知识点集锦

摘要：索引对象深拷贝网络图片转在线图片点击下载对象深拷贝对象深拷贝对象深拷贝对象深拷贝对象的深拷贝一级属性拷贝和多级属性嵌套拷贝深拷贝函数满足属性多级嵌套处理重复引用，防止死循环属性为对象，递归深度复制测试对象的深拷贝大锤一级属性深拷贝的函数特性

索引

1、对象深拷贝

2、网络图片转base64, 在线图片点击下载

3、对象深拷贝

4、对象深拷贝

5、对象深拷贝

6、对象深拷贝

1、对象的深拷贝（一级属性拷贝和多级属性嵌套拷贝）

//深拷贝函数（满足属性多级嵌套）
function deepCloneObj(sourceObj){ var obj = (sourceObj instanceof Array) ? [] : {}; for (var key in sourceObj){ var tmp = sourceObj[key]; //处理重复引用，防止死循环
        if (tmp === sourceObj){ continue; 
        } if (typeof tmp === "object"){
            obj[key] = arguments.callee(tmp); //属性为对象，递归深度复制
 } else{
            obj[key] = tmp;
        }
    } return obj;
} //

1、测试对象的深拷贝

var obj = {info:{name:"大锤"}, sign: "xxx"}; var obj2 = Object.assign({}, obj);  //一级属性深拷贝 （es6的Object.assign函数特性）
var obj3 = {...obj};            //一级属性深拷贝 (es6扩展运算符)
var obj4 =  deepCloneObj(obj);  //递归深拷贝所有层级属性
var obj5 = JSON.parse(JSON.stringify(obj)); //深拷贝所有层级属性
 console.log("obj: ", JSON.stringify(obj));
console.log("obj2: ", JSON.stringify(obj2));
console.log("obj3: ", JSON.stringify(obj3));
console.log("obj4: ", JSON.stringify(obj4));
console.log("obj5: ", JSON.stringify(obj5));
console.log(".........end..........");

setTimeout(function(){

    obj.sign = "a**b"; 
    obj.info.name = "一二三";
    console.log("
****update info ****");
    console.log("obj: ", JSON.stringify(obj));
    console.log("obj2: ", JSON.stringify(obj2));
    console.log("obj3: ", JSON.stringify(obj3));
    console.log("obj4: ", JSON.stringify(obj4));
    console.log("obj5: ", JSON.stringify(obj5));
    console.log(".........end..........");
},100); /* 打印日志结果：
obj:  {"info":{"name":"大锤"},"sign":"xxx"}
obj2:  {"info":{"name":"大锤"},"sign":"xxx"}
obj3:  {"info":{"name":"大锤"},"sign":"xxx"}
obj4:  {"info":{"name":"大锤"},"sign":"xxx"}
obj5:  {"info":{"name":"大锤"},"sign":"xxx"}
.........end..........

****update info ****
obj:  {"info":{"name":"一二三"},"sign":"a**b"}   //只拷贝了第一级属性
obj2:  {"info":{"name":"一二三"},"sign":"xxx"}   //只拷贝了第一级属性
obj3:  {"info":{"name":"一二三"},"sign":"xxx"}   //只拷贝了第一级属性
obj4:  {"info":{"name":"大锤"},"sign":"xxx"}     //所有层级深拷贝
obj5:  {"info":{"name":"大锤"},"sign":"xxx"}    //所有层级深拷贝 */

//2、测试数组的深拷贝

setTimeout(function(){
    console.log("

.....数组的深拷贝测试...."); var arr = [{name: "小明"}, true, 18]; var arr2 = Object.assign([], arr); var arr3 = [...arr2]; var arr4 = deepCloneObj(arr); var arr5 = JSON.parse(JSON.stringify(arr));

    console.log("arr: ", JSON.stringify(arr));
    console.log("arr2: ", JSON.stringify(arr2));
    console.log("arr3: ", JSON.stringify(arr3));
    console.log("arr4: ", JSON.stringify(arr4));
    console.log("arr5: ", JSON.stringify(arr5));
    console.log("......end......
");

    setTimeout(function(){

        arr[0].name = "五六七", arr[1] = false, arr[2] = 99;
        console.log("arr: ", JSON.stringify(arr));
        console.log("arr2: ", JSON.stringify(arr2));
        console.log("arr3: ", JSON.stringify(arr3));
        console.log("arr4: ", JSON.stringify(arr4));
        console.log("arr5: ", JSON.stringify(arr5));

    }, 100); /* 数组测试打印日志结果：
    .....数组的深拷贝测试....
    arr:  [{"name":"小明"},true,18]
    arr2:  [{"name":"小明"},true,18]
    arr3:  [{"name":"小明"},true,18]
    arr4:  [{"name":"小明"},true,18]
    arr5:  [{"name":"小明"},true,18]
    ......end......

    arr:  [{"name":"五六七"},false,99]
    arr2:  [{"name":"五六七"},true,18]    //只拷贝了第一级属性
    arr3:  [{"name":"五六七"},true,18]   //只拷贝了第一级属性
    arr4:  [{"name":"小明"},true,18]    //所有层级深拷贝
    arr5:  [{"name":"小明"},true,18]   //所有层级深拷贝 */ },1000);