Object.keys
I adore JavaScript objects. Love them. You're probably asking "well, why don't you marry them?" Trust me: if I could, I would. Arrays are nice and all but object keys provide another level of structure and information that is invaluable. For example, it's much faster search an object for a key than it is to search an array for value presence.
The way we've always iterated on an Object instance was always a for loops with a hasOwnProperty check which was ugly; Object.keys (not Object.prototype.keys) provides an array of Object properties!
var person = {
firstName: 'David',
lastName: 'Walsh',
// ...
};
Object.keys(person).forEach(function(trait) {
console.log('Person ', trait,': ', person[trait]);
});
If you work with JSON or simply raw JavaScript objects, and you haven't been using Object.keys, now is the time to ditch the old method for this elegant solution!
![9 Mind-Blowing WebGL Demos]()
As much as developers now loathe Flash, we're still playing a bit of catch up to natively duplicate the animation capabilities that Adobe's old technology provided us. Of course we have canvas, an awesome technology, one which I highlighted 9 mind-blowing demos. Another technology available...
![5 HTML5 APIs You Didn’t Know Existed]()
When you say or read "HTML5", you half expect exotic dancers and unicorns to walk into the room to the tune of "I'm Sexy and I Know It." Can you blame us though? We watched the fundamental APIs stagnate for so long that a basic feature...
![Optimize Your Links For Print Using CSS — Show The URL]()
When moving around from page to page in your trusty browser, you get the benefit of hovering over links and viewing the link's target URL in the status bar. When it comes to page printouts, however, this obviously isn't an option. Most website printouts...
![Send Email Notifications for Broken Images Using MooTools AJAX]()
One of the little known JavaScript events is the image onError event. This event is triggered when an image 404's out because it doesn't exist. Broken images can make your website look unprofessional and it's important to fix broken images as soon as possible.
Why don’t you use this:
for (let trait in person){console.log(trait)}@Franz,
for..in iterating over NON own properties.
Not very well supported http://caniuse.com/#feat=let
Obligatory https://babeljs.io/
Also would iterate over prototype properties.
The
for each...instatement is deprecated as the part of ECMA-357 (E4X) standard. E4X support has been removed, butfor each...inwill not be disabled and removed because of backward compatibility considerations. Consider usingfor...ofinstead. (Please refer to bug 791343.)Also: Use
const, not let. The loop creates a new context in each iteration, the loop variable therefore is constant unless your loop-code changes it.