Open ckinmind opened 7 years ago
在做FreeCodeCamp的时候遇到一个题目
var collection = { "2548": { "album": "Slippery When Wet", "artist": "Bon Jovi", "tracks": [ "Let It Rock", "You Give Love a Bad Name" ] }, "2468": { "album": "1999", "artist": "Prince", "tracks": [ "1999", "Little Red Corvette" ] }, "1245": { "artist": "Robert Palmer", "tracks": [ ] }, "5439": { "album": "ABBA Gold" } }; 要操纵这个对象,有个要求是判断某个子对象中是否有某个属性存在,比如判断”2468“中有没有叫tracks的属性存在, 我用了in,但是发现怎么返回都是false if(collection[2468].tracks in collection[2468]) //false
是我大脑短路了
collection[2468].tracks //在控制台输入,返回的是 ["1999", "Little Red Corvette"] //返回数组值,所以正确的用法是 if("tracks" in collection[2468]) //true
在做FreeCodeCamp的时候遇到一个题目