javascript嵌套对象数组的数组

Question

我一直得到TypeError：testsession.testset [0] .athletes未定义 - 我尝试了很多不同的方法，是不是有一个对象数组的数组

var testsession = {};
var testsetname = {};
var testset = [];
testsession.testsetname = testsetname;
testsession.testsetname = "week9";
testsession.testset = testset;
testsession.testset.push("400M");
testsession.testset.push("800M");

var athletes = [];
var Time = "49.2";
var AthleteID = "a92";
var athlete = { "AthleteID": AthleteID, "Time": Time};
//console.log(pointer);
testsession.testset[0].athletes = athletes;
testsession.testset[0].athletes.push(athlete)
console.log(testsession.testset[0].athletes[0]);

Answer 1

当您尝试访问testsession.testset[0]时，该条目是一个字符串。您可能至少想在访问其成员之前设置testsession.testset[0] = {};。

Answer 2

testset [0]是一个字符串。使它成为一个对象

var testsession = {};
var testsetname = {};
var testset = [];
testsession.testsetname = testsetname;
testsession.testsetname = "week9";
testsession.testset = testset;

//Earlier you pushed 400m directly which is a string hence causing the error later on
testsession.testset.push({distance: "400M"});
testsession.testset.push({distance: "800M"});

var athletes = [];
var Time = "49.2";
var AthleteID = "a92";
var athlete = { "AthleteID": AthleteID, "Time": Time};
//console.log(pointer);
testsession.testset[0].athletes = athletes;
testsession.testset[0].athletes.push(athlete)
console.log(testsession.testset[0].athletes[0]);

Answer 3

testsession.testset[0]是一个原始值，一个字符串。

因此，以下陈述不会产生您认为的影响：

testsession.testset[0].athletes = athletes;

这里发生了什么？左侧的原语没有athletes属性，但JavaScript会将其强制转换为String对象，然后将该属性分配给该临时String对象，然后该对象消失为遗忘。

所以就像从未发生过赋值一样：testsession.testset[0]将保持原始值，而原始值没有属性。

当您阅读athletes属性时，同样会再次发生：JavaScript将其强制转换为String对象，只发现该对象没有athletes属性，因此您获得undefined。

Answer 4

我认为你正在使用这样的代码。

<script >

var testsession = {};
testsession.testset = [];
testsession.testset.push({testsetname:"week9"});
testsession.testset[0].list = [];

testsession.testset[0].list.push({distance:"400M"});
testsession.testset[0].list[0].athletes = [];
testsession.testset[0].list[0].athletes.push({ AthleteID:  "a92", Time: "49.2"});

testsession.testset[0].list.push({distance:"900M"});
testsession.testset[0].list[1].athletes = [];
testsession.testset[0].list[1].athletes.push({ AthleteID:  "a93", Time: "99.2"});

console.log(testsession);

</script>

结果将是这样的：

"{"testset":[{"testsetname":"week9","list":[{"distance":"400M","athletes":[{"AthleteID":"a92","Time":"49.2"}]},{"distance":"900M","athletes":[{"AthleteID":"a93","Time":"99.2"}]}]}]}"