为什么我的返回值未定义（JavaScript）
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Why is my return value undefined (JavaScript)
提问by Ben
I have an array called questionSets full of objects. The createSet function should create new or create a copy of an existing questionSets object. The function getQuestionsFromSet is used if createSet is used to make a copy. For some reason when I call getQuestionsFromSet() from inside createSet() I always get a returned value of 'undefined'. I can't figure out why because when I do a console.log() of the value to be returned by getQuestionsFromSet() I see exactly what I want.
我有一个名为 questionSets 的数组，里面充满了对象。createSet 函数应该创建新的或创建现有 questionSets 对象的副本。如果使用 createSet 进行复制，则使用函数 getQuestionsFromSet。出于某种原因，当我从 createSet() 内部调用 getQuestionsFromSet() 时，我总是得到“未定义”的返回值。我不知道为什么，因为当我执行 getQuestionsFromSet() 返回的值的 console.log() 时，我看到了我想要的。
I have these two functions.
我有这两个功能。
function createSet(name, copiedName) {
var questions = [];
if (copiedName) {
questions = getQuestionsFromSet(copiedName);
}
console.log(questions); // undefined. WHY??
questionSets.push({
label: name,
value: questions
});
}; // end createSet()
function getQuestionsFromSet(setName) {
$.each(questionSets, function (index, obj) {
if (obj.label == setName) {
console.log(obj.value); // array with some objects as values, which is what I expect.
return obj.value;
}
});
}; // end getQuestionsFromSet()
回答by techfoobar
Because getQuestionsFromSet()does not returnanything and so is implicitly undefined.
因为getQuestionsFromSet()没有return任何东西，所以是隐式undefined。
What you need is probably something like:
你需要的可能是这样的：
function getQuestionsFromSet(setName) {
var matched = []; // the array to store matched questions..
$.each(questionSets, function (index, obj) {
if (obj.label == setName) {
console.log(obj.value); // array with some objects as values, which is what I expect.
matched.push(obj.value); // push the matched ones
}
});
return matched; // **return** it
}
回答by haim770
return obj.value;is nested within the inner $.each(function{}), and getQuestionsFromSetis indeed not returning anything.
return obj.value;嵌套在内部$.each(function{})，并且getQuestionsFromSet确实没有返回任何内容。
