JS rem 设置

(function () {
	var docEl = document.documentElement;
	var resize = 'orientationchange' in window ? 'orientationchange' : 'resize';
	var setRem = function () {

		var screenWidth = docEl.clientWidth || window.screen.width || 360;
		// 1080 PSD宽度(可变的)
		docEl.style.fontSize = (100 * screenWidth / 1080) + 'px';
	}; 

	window.addEventListener('resize', setRem, false);
	setRem();
})();

// 用法
psd量出来的像素距离 除以100  比如psd: 100px 转换后 1rem;