Javascript approach to copy properties of first array(of objects) into another array(of objects) of different lengths

Question

I have an object array say

srcObj = [{a:1, b:2}, {c:3, d:4}]

destObj = [{a:1, b:2}]

I want to copy values of this array into another array that may have a shorter length than the above srcObj array. How would I construct the loop to increase the length of destObj array depending on the size of srcObj array and then insert the missing items from srcObj array to destObj array.

Answer 1

The following code do the job:

 function containsObject(obj, list) { var i; for (i = 0; i < list.length; i++) { if (JSON.stringify(list[i]) === JSON.stringify(obj)) { return true; } } return false; } var srcObj = [{a:1, b:2}, {c:3, d:4}] var destObj = [{a:1, b:2}] for(var i = 0; i < srcObj.length; i++) { if (!containsObject(srcObj[i], destObj)){ destObj.push(srcObj[i]); } } console.log(destObj); 

If you want a more slow and more generic way to compare objects I recommend you to read the answer for the question: Object comparison in JavaScript

Answer 2

(assuming destObj.length < srcObj.length is already known)

Maybe:

var i;
while ((i = destObj.length) < srcObj.length) {
  destObj.push(srcObj[i]);
}

?

(But note it's just a shallow copy of array items, from srcObj into destObj; the "copied" object values will be in fact shared by the two arrays, by references; and this may or may not be what you want)