移动端px转换rem

function setHtmlFont(){
    var html = document.documentElement;
    window.rem = html.getBoundingClientRect().width / 750 *100;
    html.style.fontSize = window.rem + 'px';
}

setHtmlFont();

window.addEventListener('resize', function () {
	setHtmlFont();
})

//例如font-size:24px写成font-size=0.24rem