如何在 JavaScript 对象中插入一个变量作为键？
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How do I interpolate a variable as a key in a JavaScript object?
提问by Geo
How can I use the value of the variable aas a key to lookup a property? I want to be able to say: b["whatever"]and have this return 20:
如何使用变量的值a作为查找属性的键？我希望能够说：b["whatever"]并有这个回报 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":20instead of a:20where "whatever" is itself in a variable. Maybe an evalcould be used?
我在问在创建 , 的过程中是否有可能b让它包含"whatever":20而不是a:20“任何”本身在变量中的位置。也许eval可以使用？
回答by mVChr
var a = "whatever";
var b = {};
b[a] = 20;
alert(b["whatever"]); // shows 20
回答by ucstre
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。不知道其他浏览器。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，要插入一个变量，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/，作者定义的地方：
[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.
我也不确定您是否应该使用该语法。它并不广为人知。您团队中的其他成员可能不理解代码。
回答by Rocket Hazmat
var a = "whatever";
var b = {a : 20};
b[a] = 37;
alert(b["whatever"]); // 37
'a'is a string with the value 'a'. ais a variable with the value 'whatever'.
'a'是一个值为 的字符串'a'。a是一个值为 的变量'whatever'。
回答by rashadb
Great question. I had a time trying to figure this out with underscore but the answer couldn't be more simple:
很好的问题。我有一段时间试图用下划线解决这个问题，但答案再简单不过了：
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！
回答by Naftali aka Neal
Try this:
尝试这个：
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，如果我从以下评论中正确理解，请尝试以下操作：
var a = "whatever";
var b = {a : 20};
alert(b.a); // Shows 20
回答by Benny Neugebauer
To show all options, I want mention the CoffeeScriptway of doing this, which is:
为了显示所有选项，我想提及执行此操作的CoffeeScript方式，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
