如何检查JavaScript中对象数组中的索引是否存在？ [英] How can I check index in object array exist or no in javascript?

问题描述

我的JavaScript代码如下：

My javascript code like this :

<script type="text/javascript">
    var team = [{id:"1", name:"chelsea"}, {id:"3", name:"mu"}, {id:"5", name:"arsenal"}];
    for(var i = 0; i < 5; i++) {
        if(team[i].id || typeof team[i].id !== 'undefined' || team[i].id !== null) {
            console.log(team[i].id)
        }
        else {
            console.log(i+1)
        }
    }
</script>

如果代码运行，则在控制台上存在如下错误：

If the code run, on the console exist error like this :

未捕获的TypeError：无法读取未定义的属性'id'

Uncaught TypeError: Cannot read property 'id' of undefined

如果变量不存在则具有添加条件

Whereas I had add condition if the variable not exist

我该如何解决？

推荐答案

据我了解，当您在评论输出 1,2,3,4,5 之一中说时，您需要缺少ID —在您的情况下是 2,4

As I understand when you said on one of your comment output 1,2,3,4,5 that you need the missing ids -- In your case there are 2,4

var team = [{id:"1", name:"chelsea"}, {id:"3", name:"mu"}, {id:"5", name:"arsenal"}];
var empty_ids = 0;
for(var i = 0; i < 5; i++) {   
    if(team[i] && typeof team[i] !== 'undefined' && team[i] !== null) {  
        if(parseInt(team[i].id) !== i + 1){  // check if id on the array not equal the i + 1 from the loop
          for( var k= 1 ; k < parseInt(team[i].id) - empty_ids ; k++){ 
            console.log(empty_ids + k +" missing");
          }
          console.log(team[i].id);
        }else{
          console.log(team[i].id);
        }
        empty_ids = parseInt(team[i].id);
    }else{
      if(empty_ids <= i){
        console.log(empty_ids + 1 + " undefined team[i]");
        empty_ids = empty_ids + 1;
      }
      
    }
}

注意：此即使更改团队数组，代码也将起作用

Note: this code will work even if you change the team array

var team = [{id:"1", name:"chelsea"}, {id:"5", name:"arsenal"}]; 
//or 
var team = [{id:"1", name:"chelsea"}, {id:"3", name:"mu"}, {id:"4", name:"arsenal"}]; 
//or 
var team = [{id:"1", name:"chelsea"}, {id:"4", name:"arsenal"}];

所以请尝试更改 var team = 与建议的值..我添加了缺少和未定义，以使您注意到的位置console.log

So please try to change var team = with suggested values .. I added a missing and undefined to let you notice from where the console.log comes

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