In my next blog post, I'll show you how to render an array in ReactJS.
One of the most common times I need to loop over an object is when I'm rendering a list of items in ReactJS (like the tag HTML example above). you can use Object.entries to get an array of the properties for a JavaScript object. but I either get one div with all the itemList entries as one grid-item, or only the first value of each object. If you're looking to use Array.map() on an object, and don't have time to read this post - here's how you can do it. Currently I only get the first value of each object inside itemList: name description details 1 2 3 itemList. It's true that every browser supports for (duh!), but experience proved that something that iterates over a collection for us is simpler as it doesn't force us to take care of a variable for counting, while the (relatively) complex - although well-known - syntax of for is prone to mistakes.Looping over arrays is fairly easy in JavaScript, but harder with objects, because you can't use array functions like `Array.map()`. The JavaScript forEach method is one of the several ways to loop through arrays. a simple for statement would have worked. for (var key in object) console.log (key, object) sudo at 4:51 2 In modern JS Object.entries (object).forEach ( ( key, value) > console.
Quite heavy when it comes to memory consumption and CPU usage.Ĭonclusion: use document.querySelectorAll instead (which returns a NodeList). It's a live collection that gets updated when the DOM changes. and something that should be avoided in general. Now, the former does have forEach defined - but it's pretty much the only array method that has been added to its prototype so far.īut it's only a relatively recent addition, so older browsers don't support it - fortunately, the Array#forEach trick works pretty well, down to sufficiently old Internet Explorer versions (probably 6? 5.5? The heck am I saying, that could work for slice, but forEach was added only in IE9.).Ī HTMLCollection is a totally different beast. It contains well written, well thought and well explained computer science and programming articles, quizzes and practice/competitive programming/company interview Questions. But you can iterate over a JavaScript object using forEach () if you transform the object into an array first, using Object.keys (), Object.values (), or Object.entries (). A small correction: you used document.getElementsB圜lassName which does not return a NodeList but a HTMLCollection. JavaScript's ArrayforEach () function lets you iterate over an array, but not over an object.
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