I am trying to use Array.prototype.push.apply to merge two lists.
c = Array.prototype.push.apply(a, b);
However, this does not merge the arrays when the second one is [].
for instance if
a = ['x', 'y', 'z']
b = []
c will be 3
Why is this happening?
Shouldn't [] be treated like any array?
Just use Array.prototype.concat:
c = a.concat(b);
It is perfectly correct, because Array.push() will return the length of the new array.
If you want a new array which has the concatenated value then use Array.concat() instead.
What you may have been trying to achieve is using push.apply to append b to a. However this method means that you don't have to create a new array c to hold the result.
var a = [1, 2, 3, 4], b = [5];
a.push.apply(a, b); // a = [1, 2, 3, 4, 5]
Your real problem is the .apply, it ask the contetx (a) and an array of values (b), if you pass an empty array it acts like you have passed no values...
Try this:
c = Array.prototype.push.call(a, b);
//c = 4
3? What inputs did you try where it "worked"?