js動態設置fontsize大小

new function() {
	var _self = this;
	_self.width = 750;
	_self.fontSize = 100;
	_self.widthProportion = function() {
		var p = (document.body && document.body.clientWidth || document.getElementsByTagName("html")[0].offsetWidth) / _self.width;
		return p;
	};
	_self.changePage = function() {
		document.getElementsByTagName("html")[0].setAttribute("style", "font-size:" + _self.widthProportion() * _self.fontSize + "px");
	}
	_self.changePage();
	window.addEventListener('resize', function() {
		_self.changePage();
	}, false);
};