如何将变量插入JavaScript对象中作为键？

How can I use the value of the variable a as a key to lookup a property? I want to be able to say: b["whatever"] and have this return 20:

如何使用变量a的值作为查找属性的键?我希望能够说:b [“无论如何”]并获得此回报20:

var a = "whatever";
var b = {a : 20};     // Want this to assign b.whatever
alert(b["whatever"]); // so that this shows 20, not `undefined`

I am asking if it's possible during the creation of b, to have it contain "whatever":20 instead of a:20 where "whatever" is itself in a variable. Maybe an eval could be used?

我在询问是否有可能在创建b期间让它包含“无论”:20而不是:20其中“what”本身就是变量。也许可以使用eval?

7 个解决方案

#1

var a = "whatever";
var b = {};
b[a] = 20;
alert(b["whatever"]); // shows 20

#2

This works in Firefox 39 and Chrome 44. Don't know about other browsers. Also it doesn't work in nodejs v0.12.7.

这适用于Firefox 39和Chrome 44.不了解其他浏览器。它也不适用于nodejs v0.12.7。

var a = "whatever";
var b = { [a]: 20 };
console.log(b["whatever"]); // shows 20

That is, to interpolate a variable, enclose it in brackets.

也就是说,要插入变量,请将其括在括号中。

I'm not sure if this is a part of any standard. Originally, I saw such syntax here: https://hacks.mozilla.org/2015/07/es6-in-depth-classes/ where the author defined:

我不确定这是否是任何标准的一部分。最初,我在这里看到了这样的语法:https://hacks.mozilla.org/2015/07/es6-in-depth-classes/作者定义:

[functionThatReturnsPropertyName()] (args) { ... }

I'm also not sure if you should use that syntax. It's not widely known. Other members on your team might not understand the code.

我也不确定你是否应该使用这种语法。它并不广为人知。您团队中的其他成员可能无法理解代码。

#3

var a = "whatever";
var b = {a : 20};
b[a] = 37;
alert(b["whatever"]); // 37

'a' is a string with the value 'a'. a is a variable with the value 'whatever'.

'a'是一个值为'a'的字符串。 a是值为'whatever'的变量。

#4

Great question. I had a time trying to figure this out with underscore but the answer couldn't be more simple:

好问题。我有时间试图用下划线来解决这个问题,但答案不能简单:

var a = "whatever";
var b = {a : 20};

var array = [a, b]
var answer = _.object([[array]])// {whatever: {a:20}}//NOTICE THE DOUBLE SET OF BRACKETS AROUND [[array]]

I hope this helps!

我希望这有帮助!

#5

Try this:

var a = "whatever";
var c = "something";
var b = {whatever : 20, something: 37};
alert(b[a]); // Shows 20
alert(b[c]); // Shows 37

Here is the fiddle.

这是小提琴。

Or if I understand from the below comments correctly, try this:

或者,如果我从下面的评论中正确理解,请尝试以下方法:

var a = "whatever";
var b = {a : 20};
alert(b.a); // Shows 20

#6

To show all options, I want mention the CoffeeScript way of doing this, which is:

为了显示所有选项,我想提一下CoffeeScript的做法,即:

var a = "whatever";
var b = (
  obj = {},
  obj["" + a] = 20,
  obj
);

alert(b.whatever); // 20

Although I prefer:

虽然我更喜欢:

var a = "whatever";
var b = {};
b[a] = 20;

alert(b.whatever); // 20

#7

What if it is

如果它是什么

var a = "whatever.other";
var b = {a:20};
expected output b["whatever"]["other"] should return 20

#1

var a = "whatever";
var b = {};
b[a] = 20;
alert(b["whatever"]); // shows 20

#2