I have a <div> with some child <div> in it. E.g.

<div id=niceParent>

  <div></div>

  <div></div>

  <div></div>

  <div></div>

</div>

I tried to loop through them with the forEach function, because I thought that document.getElementById(niceParent).children is an array, as I can access the elements with

console.log(document.getElementById(niceParent).children[1]);

console.log(document.getElementById(niceParent).children[2]);

console.log(document.getElementById(niceParent).children[3]);

console.log(document.getElementById(niceParent).children[4]);

Hence I tried

document.getElementById(niceParent).children.forEach(function(entry) {

  console.log(entry);

});

which is not working. I get

TypeError: document.getElementById(...).children.forEach is not a function

As a workaround I also tried it with a—much more complicated—for..in loop:

for (var i in document.getElementById(niceParent).children) {

  if (document.getElementById(niceParent).children[i].nodeType == 1) console.log(document.getElementById(niceParent).children[i]);

}

which worked as expected.

Why?