Use a variable for the index of an array in javascript

Question

Here is my code:

var span = getSpanWithClass("galleria-current");
var slideNumber = span.innerHTML
var imageIDDivs = document.getElementsByClassName("slideshowImage");
var singleimageidDiv = imageIDDivs[slideNumber]

If I use this, sigleImageidDiv doesn't have anything in it. If I just put 0 or 1 in like this:

var singleimageidDiv = imageIDDivs[1]

It works fine. slideNumber is 1, in my test cases.

I have tried these as well:

var singleimageidDiv = imageIDDivs[Number(slideNumber)]

var singleimageidDiv = imageIDDivs[parseInt(slideNumber)]

What is the proper way to use a variable as the index of an array?

Answer 1

Parse to int with a radix.

This is the proper way of doing it:

imageIDDivs[parseInt(slideNumber, 10)];

Live DEMO If it doesn't work, then your problem is somewhere else.

---

BTW indexes work with strings as well. DEMO

Answer 2

innerHTML returns the string inside the element, so if even if you have a number inside your element, it'll be returned as a string, that's why when you use that variable as an index for your array, you don't get a result. Using parseInt is an acceptable solution, you could also just do something like span.innerHTML * 1, that would force JS to treat the string as an integer.

Answer 3

I think, you have an error in your getSpanWithClass function.