javascript - Inline object literal with a variable property - Stack Overflow

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Why does Javascript syntax not support inline object literals with a variable property? For example:

const f = function (arg) {
  console.log(arg);
}

f({}['some key'] = 1) // 1
f({ 'some key' : 1})  // [object Object] { some key: 1 }

Is there another alternative other than the two steps?

var o = {}
o['some key'] = 1
f(o)

Thanks!

Why does Javascript syntax not support inline object literals with a variable property? For example:

const f = function (arg) {
  console.log(arg);
}

f({}['some key'] = 1) // 1
f({ 'some key' : 1})  // [object Object] { some key: 1 }

Is there another alternative other than the two steps?

var o = {}
o['some key'] = 1
f(o)

Thanks!

• javascript

Share Follow asked Dec 10, 2015 at 14:15 donnie_armstrongdonnie_armstrong 1,38333 gold badges1111 silver badges88 bronze badges 2

• is there a problem with var o = { 'some key' : 1} ? if you mean property name contained in variable it's ES6 – Hacketo Commented Dec 10, 2015 at 14:25
• Correct, sorry that is not reflected in the example. – donnie_armstrong Commented Dec 10, 2015 at 14:31

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1 Answer 1

Sorted by: Reset to default 11

Why does Javascript syntax not support inline object literals with a variable property?

You seem to be asking about variable properties, yet your examples do not use variables. Specifically, this example will work just fine.

f({ 'some key' : 1})

However, if you actually did want to use a variable without first creating the object, ECMAScript 6 now allows this.

So if this is your variable:

var my_variable = 'some key';

You can now use square brackets around the property name in the object literal, and it will use the value of the expression you provide:

var o = {[my_variable]: 1};

The o object will have a property named "some key". This only works in the implementations that support this syntax of course.

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