( function ( doc, win ) {

	// 监听 orientation changes
	var angle, dir;
	if ( "orientation" in screen ) {
		angle == screen.orientation.angle;
	} else if ( "orientation" in window ) {
		angle = window.orientation.angle;
	} else { angle = 0; }
	dir = 0


	window.addEventListener( "orientationchange", function ( event ) {

		// 根据event.orientation|screen.orientation.angle等于0|180、90|-90度来判断横竖屏
		//alert( screen.orientation.angle );
		if ( dir == 90 || dir == -90 ) {
			dir = 1;
		}

	}, false );

	var docEl = doc.documentElement;         //documentElement 属性是根节点
	resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize';
	recalc = function () {
		var body = document.getElementsByTagName( 'body' )[ 0 ];
		var bodyClass = body.className;
		var designWidth = 1903;
		if ( bodyClass.indexOf( "mobile" ) !== -1 ) {
			if ( dir == 0 ) {
				designWidth = 375;
			} else {
				designWidth = 1903;
			}


		} else {
			designWidth = 1903;
		}
		var clientWidth = docEl.clientWidth;


		if ( !clientWidth ) return;
		docEl.style.fontSize = 10 * ( clientWidth / designWidth ) + 'px';//设置html根元素的font-size

	};

	if ( !doc.addEventListener ) return;
	win.addEventListener( resizeEvt, recalc, true );
	doc.addEventListener( 'DOMContentLoaded', recalc, false );

} )( document, window );