Javascript:循环使用TypeError属性未定义的对象 [英] Javascript: Looping an object with TypeError property undefined

问题描述

我有一个名为 xs 的对象数组，该对象存储名称

I have an array of object called xs that store name

xs = [
    {name: "Peter"},
    {name: "Doe"},
    {name: "Parker"},
    {name: "John"}
];

并且我有一个setEmptyStr函数，如果未定义变量，该函数将返回空字符串

and i have a function setEmptyStr that return empty string if variable is undefined

function setEmptyStr(v) {
  if(typeof v !== 'undefined'){
    return v;
  } else {
    return '';
  }
}

我尝试循环我的对象数组(长度比其自身数组长)，我的数组长度为4，我尝试5，并且我不想使用array.length;

I try to looping my array of object (with more length than the array it self), my array length is 4, i try 5. and i dont wanna use array.length;

for (var i = 0; i < 5; i++) {
    console.log(setEmptyStr(xs[i].name));
}

这四个名称返回成功，因为它不是未定义的.但是第五个就是返回

the 4 names are return successful because it is not undefined. But the 5th is return

TypeError属性名称"未定义.

TypeError property 'name' is undefined.

>>Peter
>>Doe
>>Parker
>>John

未捕获的TypeError:无法读取未定义的属性名称"

Uncaught TypeError: Cannot read property 'name' of undefined

我希望5号返回一个空字符串.我怎样才能做到这一点?我的代码有错误吗?

I want the 5th is return an empty string. How can i do this? Is there is an error in my code?

>>Peter
>>Doe
>>Parker
>>John
>>""

推荐答案

使用此:

xs = [
    {name: "Peter"},
    {name: "Doe"},
    {name: "Parker"},
    {name: "John"}
];

for (var i = 0; i < 5; i++) {
  console.log(setEmptyStr(xs[i] && xs[i].name));
}

function setEmptyStr(v) {
  if (typeof v !== 'undefined') {
    return v;
  } else {
    return '';
  }
}

首先测试 xs [i] 可以防止错误尝试访问 undefined 的属性.

Testing xs[i] first prevents an error from trying to access a property of undefined.

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