我们如何访问对象数组的属性？ （打字稿）

Question

let array = [{id:1},{id:1},{id:1},{id:1},{id:1}];
console.log(array[0].id);

显示的ID不存在？？

答案是我们需要定义array = [any];

Answer 1

尝试一下：

 for( let i=0;i<array.length;i++){
     cosole.log(array[i].id);
    }

Answer 2

您的问题有点令人困惑！

  

显示的ID不存在？？

array [0] .id将返回1；

Answer 3

您可以尝试

console.log(array[0]['id']);

Answer 4

这似乎是正确的，也许您没有正确输出值，请参见此处的代码：CODE

打字稿

array_t(){
    let array = [{id:1},{id:5},{id:1},{id:1},{id:1}];
    return array[0].id.toString() + array[1].id.toString();
    }

array(){
    let array = [{id:1},{id:5},{id:1},{id:1},{id:1}];
    return array[0].id + array[1].id;
}

HTML

<br>
<div>{{ array() }}</div>
<br>
<div>{{ array_t() }}</div>

Answer 5

尝试一下，它将起作用

constructor(){
    let   array = [{id:1},{id:1},{id:1},{id:1},{id:1}];
    console.log(array[0].id )
  }

Answer 6

要访问对象数组中id项的属性n-th，可以执行以下操作：

a[n].id
// or
a[n]['id']

要检查数组中的n-th项目是否为undefined（又称不存在），请在访问id属性之前使用：

a[n] && a[n].id
// or if you want a default value in case it doesn't exist
a[n] ? a[n].id : "not found"

要打印值，可以使用console.log。

请参见代码段

const array = [{id: 1}, {id: 1}, {id: 1}, {id: 1}, {id: 1}];

// Accessing element in position 0
console.log(array[0]);

// Accessing the id of the element in position 0
console.log(array[0].id)
console.log(array[0]['id'])


// Accessing the id of the element in position 0 after checking its existence
console.log(array[0] && array[0].id)

// Accessing the id of the element in position 0 after checking its existence
// and returning a default value if it is not defined
console.log(array[0] ? array[0].id : "not found")

// Same as above but with an undefined value
console.log(array[99] ? array[99].id : "not found")