Fit font-size in container's width

jquery-fontsize-fit.js

$.fn.fitFontSize = function(minFontSize, containerWidth){
    minFontSize = minFontSize || 12;
    return this.each(function(){
        var $this = $(this);
  var sectionWidth = containerWidth || $this.parent().innerWidth();
        var spanWidth = $this.width();
        var newFontSize = (sectionWidth/spanWidth) * minFontSize;
        $this.css({"font-size" : newFontSize, "line-height" : (newFontSize+2) + "px"});
    });
};