我如何获取数组的所有索引

Question

如何获取数组的所有索引，

[  
   {  
      "name":"aloha",
      "age":"18"
   },
   {  
      "name":"hello word"
   },
   {  
      "name":"John Doe",
      "age":"28"
   }
]

输出应类似于[0,1,2]

Answer 1

最简单的方法是（请参见this post）：

let a = [{1: 'x'}, {1: 'y'}, {1: 'z'}]
let b = Array.from(a.keys())
console.log(b)

而朴素的解决方案是在数组上调用map((_, i) => i))：

let a = [{1: 'x'}, {1: 'y'}, {1: 'z'}]
let b = a.map((_, i) => i)
console.log(b)

Answer 2

您还可以使用Object.keys来检查任何对象的键索引。

let a = [
        {
        'name' : "aloha",
        "age": "18"
        },
        {
        "name": "hello word"
        },
        {
        "name": "John Doe",
        "age" : "28"
    }]
    
console.log(Object.keys(a));

Answer 3

您可以使用forEach循环，例如以下示例：

//The array you want to get all the indexes from
const array = [{'a':1}, {'b':2}, {'c':3}];
//All indexes array
const indexArray = [];

array.forEach((el, i) => {
    indexArray.push(i);
});

Answer 4

let ary = [
  {
  'name' : "aloha",
  "age": "18"
  },
  {
   "name": "hello word"
  },
  {
   "name": "John Doe",
   "age" : "28"
  }
]

 let outputAry = Array.from(Array(ary.length),(x,index)=>index);
 console.log(outputAry);