Remove all child elements of a DOM node in JavaScript

Option 1 A: Clearing innerHTML.

• This approach is simple, but might not be suitable for high-performance applications because it invokes the browser's HTML parser (though browsers may optimize for the case where the value is an empty string).

doFoo.onclick = () => {
  const myNode = document.getElementById("foo");
  myNode.innerHTML = '';
}

<div id='foo' style="height: 100px; width: 100px; border: 1px solid black;">
  <span>Hello</span>
</div>
<button id='doFoo'>Remove via innerHTML</button>

Option 1 B: Clearing textContent

• As above, but use .textContent. According to MDN this will be faster than innerHTML as browsers won't invoke their HTML parsers and will instead immediately replace all children of the element with a single #text node.

doFoo.onclick = () => {
  const myNode = document.getElementById("foo");
  myNode.textContent = '';
}

<div id='foo' style="height: 100px; width: 100px; border: 1px solid black;">
  <span>Hello</span>
</div>
<button id='doFoo'>Remove via textContent</button>

Option 2 A: Looping to remove every lastChild:

• An earlier edit to this answer used firstChild, but this is updated to use lastChild as in computer-science, in general, it's significantly faster to remove the last element of a collection than it is to remove the first element (depending on how the collection is implemented).
• The loop continues to check for firstChild just in case it's faster to check for firstChild than lastChild (e.g. if the element list is implemented as a directed linked-list by the UA).

doFoo.onclick = () => {
  const myNode = document.getElementById("foo");
  while (myNode.firstChild) {
    myNode.removeChild(myNode.lastChild);
  }
}

<div id='foo' style="height: 100px; width: 100px; border: 1px solid black;">
  <span>Hello</span>
</div>
<button id='doFoo'>Remove via lastChild-loop</button>

Option 2 B: Looping to remove every lastElementChild:

• This approach preserves all non-Element (namely #text nodes and <!-- comments --> ) children of the parent (but not their descendants) - and this may be desirable in your application (e.g. some templating systems that use inline HTML comments to store template instructions).
• This approach wasn't used until recent years as Internet Explorer only added support for lastElementChild in IE9.

doFoo.onclick = () => {
  const myNode = document.getElementById("foo");
  while (myNode.lastElementChild) {
    myNode.removeChild(myNode.lastElementChild);
  }
}

<div id='foo' style="height: 100px; width: 100px; border: 1px solid black;">
  <!-- This comment won't be removed -->
  <span>Hello <!-- This comment WILL be removed --></span>
  <!-- But this one won't. -->
</div>
<button id='doFoo'>Remove via lastElementChild-loop</button>

Bonus: Element.clearChildren monkey-patch:

• We can add a new method-property to the Element prototype in JavaScript to simplify invoking it to just el.clearChildren() (where el is any HTML element object).
• (Strictly speaking this is a monkey-patch, not a polyfill, as this is not a standard DOM feature or missing feature. Note that monkey-patching is rightfully discouraged in many situations.)

if( typeof Element.prototype.clearChildren === 'undefined' ) {
    Object.defineProperty(Element.prototype, 'clearChildren', {
      configurable: true,
      enumerable: false,
      value: function() {
        while(this.firstChild) this.removeChild(this.lastChild);
      }
    });
}

<div id='foo' style="height: 100px; width: 100px; border: 1px solid black;">
  <span>Hello <!-- This comment WILL be removed --></span>
</div>
<button onclick="this.previousElementSibling.clearChildren()">Remove via monkey-patch</button>

Use modern Javascript, with remove!

const parent = document.getElementById("foo")
while (parent.firstChild) {
    parent.firstChild.remove()
}

This is a newer way to write node removal in ES5. It is vanilla JS and reads much nicer than relying on parent.

All modern browsers are supported.

Browser Support - 97% Jun '21