Strange JavaScript Object syntax

Question

I recently came accross this in a Library called WebApp.net:

var $h = {
    get HEAD() { return 0 },
    get BACK() { return 1 },
    get HOME() { return 2 },
    get LEFT() { return 3 },
    get RIGHT() { return 4 },
    get TITLE() { return 5 }
};
var $d = {
    get L2R() { return +1 },
    get R2L() { return -1 }
};

I'm familar with JS, but this seems to make no sense. Chrome does interpret this as Object with $h.HEAD and the others set as numbers which come after the return. Additionally, something like getters are part of $h, too.

Can anybody give me more info about this? IE cannot interpret this, so I have to make an equivalent to this.

It's an object containing getters. Works also in IE>8.

Teemu
– Teemu

2015-05-25 15:31:13 +00:00
Commented May 25, 2015 at 15:31 — Teemu
– Teemu, Commented May 25, 2015 at 15:31
@Teemu: make it an answer

slebetman
– slebetman

2015-05-25 15:43:22 +00:00
Commented May 25, 2015 at 15:43 — slebetman
– slebetman, Commented May 25, 2015 at 15:43

Teemu · Accepted Answer · 2015-05-25 16:03:10Z

6

You've found getters.

With a getter you can execute a function, when you're reading a property of an object. Also it is a way to give some protection to object properties, you can't change the value of a getter directly.

Getters and setters are implemented also in IE since IE9.

edited May 25, 2015 at 16:03

answered May 25, 2015 at 15:49

Teemu

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2 Comments

sja Over a year ago

You're right, thanks. I was surprised to came accross such a "modern" feature in such an old code. My IE problem was because of compat mode in IE11 wich is mostly like IE8. There it's not available.

Teemu Over a year ago

@sja I don't know, how old WebApp.net is, but in FF getters and setters are supported since 2.0, which has been released in 2006.

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