javascriptloopschildren

Loop through childNodes

I'm trying to loop through childNodes like this:

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

However, it output Uncaught TypeError: undefined is not a function due to forEach function. I also try to use children instead of childNodes but nothing changed.

Does anybody know what's going on?

Solution

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

    Every major browser supports nodeList.forEach

    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) {});

    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 ];

    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);
});

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