引用数据类型的深拷贝

let cloneObj = function(obj){
    let str, newobj = obj.constructor === Array ? [] : {};
    if(typeof obj !== ‘object‘){
        return;
    } else if(window.JSON){
        str = JSON.stringify(obj), //系列化对象
        newobj = JSON.parse(str); //还原
    } else {
        for(var i in obj){
            newobj[i] = typeof obj[i] === ‘object‘ ?  cloneObj(obj[i]) : obj[i]; 
        }
    }
    return newobj;
};

let arr2 = cloneObj(arr1);

let arr2 = JSON.parse(JSON.stringify(arr1));