When you use a string variable to set a properties name why would it ever use the name of the variable itself instead?

Question

We are using some new ECMAScript stuff so I don't know if that's what's going on. Basically I do:

var key = "foo";
var obj = { key: "abc" };

and it created and obj.key property instead of an obj.foo property.

This is how JavaScript worked since the beginning... – Felix Kling Jun 06 '16 at 20:39 — Felix Kling, Jun 06 '16 at 20:39

score 2 · Accepted Answer · answered Jun 06 '16 at 20:30

2

That's a property name, not an expression that can be a variable.

In ES6, you can make it an expression:

var obj = { [key]: "abc" };

answered Jun 06 '16 at 20:30

SLaks

Whoa dude. That worked. I am completely confused about what just happened though. What do the brackets do? – Jun 06 '16 at 20:35
1

@dolphonebubleine: It makes the interpreter evaluate the character sequence `key` instead of taking it literally. – Felix Kling Jun 06 '16 at 20:40
So it is an ecmascript thing? Is there a name for this type of behavior so I can read more about it? edit - nm. Just realized what is going on. duh. It's creating a literal and not using my key variable. – Jun 06 '16 at 20:52
1

@dolphonebubleine: The ES6 feature is called "computed property names". – Bergi Jun 06 '16 at 21:06

1 Answers1