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!
![5 Awesome New Mozilla Technologies You’ve Never Heard Of]()
My trip to Mozilla Summit 2013 was incredible. I've spent so much time focusing on my project that I had lost sight of all of the great work Mozillians were putting out. MozSummit provided the perfect reminder of how brilliant my colleagues are and how much...
![I’m an Impostor]()
This is the hardest thing I've ever had to write, much less admit to myself. I've written resignation letters from jobs I've loved, I've ended relationships, I've failed at a host of tasks, and let myself down in my life. All of those feelings were very...
![MooTools Equal Heights Plugin: Equalizer]()
Keeping equal heights between elements within the same container can be hugely important for the sake of a pretty page. Unfortunately sometimes keeping columns the same height can't be done with CSS -- you need a little help from your JavaScript friends. Well...now you're...
![Dress Up Your Select Elements with FauxSelect]()
I received an email from Ben Delaney a few weeks back about an interesting MooTools script he had written. His script was called FauxSelect and took a list of elements (UL / LI) and transformed it into a beautiful Mac-like SELECT element.
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.