If your array of object is already empty, make sure it has at least one object, or that object in which you are going to push data to. Let's say, our array is myArray[], so this is now empty array, the JS engine does not know what type of data does it have, not string, not object, not number nothing. So, we are going to push an object (maybe ...

The ".apply" has to check each index in the array and convert it to a set of arguments before passing it to Array.prototype.push. Then, Array.prototype.push has to additionally allocate more memory each time, and (for some browser implementations) maybe even recalculate some position-lookup data for sparseness.

Dec 9, 2008 · The result of .push in the scenario will be = [ar1, [ar2]]. .concat solves that problem, but with sacrifice of speed and a new array created. To use .push properly in array appends, loop out the contained element first and push each. ar2.forEach(each => { ar1.push(each); }); –

Feb 25, 2009 · So in this way we can return a new array (will be a cool functional way - more much better than using push or splice) with the element inserted at index, and if the index is greater than the length of the array it will be inserted at the end.

May 16, 2017 · arry.splice(1, 0, sub_array_1); The result will be: [9,[1,2,2,2,2],8,7] On the other hand, if you are trying to insert the contents of sub_array_1 before the second element of arry, you can do something like this: Array.prototype.splice.apply(arry, [1, 0].concat(sub_array_1)); The result will be: [9,1,2,2,2,2,8,7] Here is a more general function:

Actually, all unshift/push and shift/pop mutate the source array. The unshift/push add an item to the existed array from begin/end and shift/pop remove an item from the beginning/end of an array. But there are few ways to add items to an array without a mutation. the result is a new array, to add to the end of array use below code:

Sometimes .concat() is better than .push() since .concat() returns the new array whereas .push() returns the length of the array. Therefore, if you are setting a variable equal to the result, use .concat() .

Oct 24, 2011 · In JavaScript, the type of key/value store you are attempting to use is an object literal, rather than an array. You are mistakenly creating a composite array object, which happens to have other properties based on the key names you provided, but …

push(number, value, context, content) { array.push({ number: number, value: value, context: context, content: content }) } Is there anyway, I can make sure, that the key content is only added to the element, if the content (the function gets as parameter) is not null.

Apr 19, 2016 · so not sure if this answers your question but the indexOf the items you are adding keep returning -1. Not to familiar with js but it appears the items do that because they are not in the array yet.