JavaScript的嵌套阵列

我keepy得到类型错误：testsession.testset [0] .athletes是未定义 - 我已经尝试许多不同的方式，是它不可能有对象的数组的数组JavaScript的嵌套阵列

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]);

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2017-07-29 Banry Banry

testset [0]是一个字符串。使其成为一个对象

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]);

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2017-07-29 09:58:32 Kamesh

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

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2017-07-29 09:56:54 Stephan

testsession.testset[0]是一个原始值，一个字符串。

下面的语句，因此不会造成你可能会认为它具有这样的效果：

testsession.testset[0].athletes = athletes;

这里会发生什么？左侧的图元没有athletes属性，但JavaScript会将其强制为String对象，然后将该属性分配给该临时对象，然后该对象消失并遗忘。

所以它就像是从未发生过任务：testsession.testset[0]将保持原始值，原始值没有任何属性。

当你阅读athletes属性，同样会再次发生：JavaScript的它强制转换为String对象，才发现对象有没有athletes属性，让您得到undefined。

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2017-07-29 10:00:01 trincot

我认为你是这样工作的代码。

<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>

和结果将是这样的：

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

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2017-07-29 10:05:43

JavaScript的嵌套阵列

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