Edge Animate CC :: Changing CSS Property Through External JavaScript File?

I'm trying to create all kinds of functions on an external .js file, so I can just call them in Edge multiple times with less coding. The thing is, after importing jQuery and my external Javascript file, some code works, but I get stuck at this part: changing the .css property of a symbol, more specifically, the "font-size" property. My current function is:
 
function setFont(textid,fontsize,originalWinWidth){ //textid: symbol's name; fontsize: current font size of this symbol; originalWinWidth: window size at the start of the animation
console.log("Set Font:");
//set the original font size
var originalFontSize = Math.round(originalWinWidth/fontsize);
console.log("Original Font Size: " + originalFontSize);
console.log("Text ID: " + textid);
//set the font size using jquery
sym.$(textid).css("font-size", originalFontSize);  }
 
I get an error at the last line, all other parts of the code works.