Loop through childNodes

Here is how you can do it with for-in loop.

var children = element.childNodes;

for(child in children){
    console.log(children[child]);
}

I'm very late to the party, but since element.lastChild.nextSibling === null, the following seems like the most straightforward option to me:

for(var child=element.firstChild; child!==null; child=child.nextSibling) {
    console.log(child);
}

The variable children is a NodeList instance and NodeLists are not true Array and therefore they do not inherit the forEach method.

Also some browsers actually support it nodeList.forEach

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ES5

You can use slice from Array to convert the NodeList into a proper Array.

var array = Array.prototype.slice.call(children);

You could also simply use call to invoke forEach and pass it the NodeList as context.

[].forEach.call(children, function(child) {});

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ES6

You can use the from method to convert your NodeList into an Array.

var array = Array.from(children);

Or you can also use the spread syntax ... like so

let array = [ ...children ];

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A hack that can be used is NodeList.prototype.forEach = Array.prototype.forEach and you can then use forEach with any NodeList without having to convert them each time.

NodeList.prototype.forEach = Array.prototype.forEach
var children = element.childNodes;
children.forEach(function(item){
    console.log(item);
});

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See A comprehensive dive into NodeLists, Arrays, converting NodeLists and understanding the DOM for a good explanation and other ways to do it.