Loop Over querySelectorAll Matches

You can loop over Arrays really easily in JavaScript with forEach, but unfortunately it's not that simple with the results of a querySelectorAll.

/* Will Not Work */
document.querySelectorAll('.module').forEach(function(){
  
});

That's because what you get back from querySelectorAll isn't an Array, it's a (non-live) NodeList.

Here's a quick way to iterate over all the found elements though:

var divs = document.querySelectorAll('div );

[].forEach.call(divs, function(div) {
  // do whatever
  div.style.color = "red";
});

You could also use a classic for loop:

var divs = document.querySelectorAll('div'), i;

for (i = 0; i < divs.length; ++i) {
  divs[i].style.color = "green";
}

There are also for..of loops, but...

/* Be warned, this only works in Firefox */

var divs = document.querySelectorAll('div );

for (var div of divs) {
  div.style.color = "blue";
}

This is pretty intense (probably dangerous and generally not recommended) but you could make NodeList have the same forEach function as Array does, then use it.

NodeList.prototype.forEach = Array.prototype.forEach;

var divs = document.querySelectorAll('div').forEach(function(el) {
  el.style.color = "orange";
})

There is a bit more information in the MDN article.