June 2018
Beginner
288 pages
6h 31m
English
Content preview from Rediscovering JavaScriptBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Symbol—A New Primitive Type
JavaScript previously had five primitive types: number, string, boolean, null, and, undefined; now it has one more. Symbol is a new primitive type in JavaScript intended for limited specialized use. Symbols can be used for three distinct purposes:
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To define properties for objects in such a way they don’t appear during normal iteration—these properties are not private; they’re just not easily discovered like other properties.
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To easily define a global registry or dictionary of objects.
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To define some special well-known methods in objects; this feature, which fills the void of interfaces, is arguably one of the most important purposes of Symbol.
Interfaces in languages like Java and C# are useful for design by contract ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.