This can be done easily using Regular expressions.

Following are the sequence of steps to be done:

1. Step1 is to covert the entire string to the lower case letter. Although URLs are case insensitive, it looks good if the entire string has lower case letters.
2. Step 2 is to remove characters from the title other than alphanumeric and space.
3. Step3 is to replace a space with "-"

Let's write a function in JS that takes a title as an input and returns the URL slug as an output.

<html>
<script>
function TitleToSlug(){
var Title = document.getElementById("title").value;
var output =  Title.toLowerCase();
output = output.replace(/[^\w ]+/g, '');
output = output.replace(/ +/g, '-');
document.getElementById("output").textContent = output;

}
</script>
<html>