Jump Start JavaScript by Ara Pehlivanian Don Nguyen

Author:Ara Pehlivanian, Don Nguyen [Pehlivanian, Ara]
Language: eng
Format: epub, mobi, pdf
ISBN: 9780987332189
Publisher: SitePoint Pty. Ltd.
Published: 2013-03-25T16:00:00+00:00

The for ... in Loop

The for ... in loop was covered in the last chapter. To recap, this statement is used to loop through the properties of an object; for example:

for-in.html (excerpt)

var agents = { '005': "Michael Harp", '006': "John Smith", '007': "James Bond" }; for (key in agents) { if ('007' === key) { console.log('Bond, ' + agents[key] + ' ↵has been found!'); } else { console.log('Standard spy, ' + agents[key] + ' ↵has been found'); } }

There are a few important points worth keeping in mind. First, avoid using this with arrays; instead, use the standard for loop. Second, do not rely on the loop returning objects in the same order in which they were defined. Although most vendors do implement the loop in this way, it’s not actually part of the specification, so there’s potential a standards-compliant vendor may decide on a different implementation.

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