document.queryselector
<div id="foobar"></div>
<div id="foo:bar"></div>
<script>
console.log('#foobar'); // "#fooar" (b is the backspace control character)
document.querySelector('#foobar'); // Does not match anything
console.log('#foo\bar'); // "#foobar"
console.log('#foo\\bar'); // "#foo\bar"
document.querySelector('#foo\\bar'); // Match the first div
document.querySelector('#foo:bar'); // Does not match anything
document.querySelector('#foo\:bar'); // Match the second div
</script>