Array.map:获取要在返回函数中使用的每个元素的索引 [英] Array.map : get the index of each element to use in the return function

问题描述

我正在寻找一个返回元素索引的命令，以便可以在地图函数中使用它.

I'm looking for a command that returns the index of an element so I can use it in map functions.

这是一个例子:

function myFunction() {
  var a = [4,7,9];
  //Looking for a way to return ["index 0 : 4", "index 1 : 7", "index 2 : 9"]
  //Only workaround found so far :
  var i = -1;
  Logger.log(a.map(function(el) {i++; return "index " + i + " : " + el}));
}

我敢肯定，有一条更整洁的命令可以给我元素的索引，但是到目前为止，我所有的Google搜索都没有结果.

I'm sure there's a neater way with a command that would give me the element's index, but all my google searches have been fruitless so far.

推荐答案

您可以通过以下三个步骤使它更干净:

You can make it cleaner by three steps:

• 使用传递给 map()的回调的第二个参数，即元素的索引.
• 使用箭头函数并隐式返回值
• 一次又一次地使用模板字符串而不是 + .

• Use the second parameter of callback passed to map() which is index of element.
• Use arrow function and implicitly return the value
• Use Template Strings instead of + again and again.

var a = [4,7,9];
let res = a.map((x,i) => `index ${i} : ${x}`);
console.log(res)

在上面的代码中，您创建了一个没有任何意义的函数.该函数应将数组作为参数，然后记录该特定arr的值.

In your above code you have created a function which doesn't make any sense. That function should take an array as a parameter and then log the value of that particular arr.

const myFunction = arr => console.log(arr.map((x,i) => `index ${i} : ${x}`));
myFunction([4,7,9])

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