Try this to replace multiple spaces with a single space.
<script type="text/javascript">
var myStr = "The dog has a long tail, and it is RED!";
alert(myStr); // Output 'The dog has a long tail, and it is RED!'
var newStr = myStr.replace(/ +/g, ' ');
alert(newStr); // Output 'The dog has a long tail, and it is RED!'
</script>
Read more @ Replacing Multiple Spaces with Single Space