I'm making a Google Chrome Extension and using JavaScript to check the amount of characters in the body of a website. I want it to print the amount of characters in the body, with the exception of any spaces, <style>s, and <script>s. When I enter the code below, though, I get the error "Uncaught ReferenceError: $ is not defined". I've tried removing the filter section, and it still doesn't accept the $. When I remove the $ and just use body.contents() it no longer recognizes contents() as a function, which makes sense. I was wondering what a good fix for this error is.

var length = $("body").contents().filter(function(){
  return (this.localName != "script" && this.localName != "style") ? true : false;
}).text().replace(/\s+/g, "").length;
document.write(length);