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javascriptobjectscopethiscurly-braces

Question about "this" in JavaScript

This may be a newbie question. I've used javascript for years but have only started to get "serious" about it. I have a question about "this"

var defaults = {
    baseId : 'item_',
    baseName : this.baseId
}

console.log('defaults',defaults);

Not sure why defaults.baseName is "undefined" How does one reference stuff in the curly braces? Is it possible, or do I really have to type 'item_' twice?

Solution

  • JavaScript object literal is a syntatic sugar therefore it does not work.

    this; // at point A
var defaults = {
    baseId : 'item_',
    baseName : this.baseId
}

    translates to

    this; // point A
var defaults = new Object();
defaults.baseId = 'item_';
defaults.baseName = this.baseId; // "this" here is same as "this" at point A

    You can use getters and setters.

    {
   baseId: 'item_',
   get baseName() { return this.baseId; },
   set baseName(x) { this.baseId = x }
}