我怎样才能获得所有数组索引

Question

我如何获得所有数组索引，

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

输出应该像[0,1,2]

Answer 1

最简单的方法是（见这篇文章 ）：

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

天真的解决方案是在你的数组上调用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，如下例所示：

//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);