移动端响应式js代码

(function() {    var b = document.documentElement,            a = function() {                var a = b.getBoundingClientRect().width;                b.style.fontSize = .0625 * (640 <= a ? 640 : a) + "px"            },            c = null;    window.addEventListener("resize",            function() {                clearTimeout(c);                c = setTimeout(a, 300)            });    a()})();