用JS控制页面等比例缩小的实现方法

window.addEventListener('load', adaptation);
window.addEventListener('resize', adaptation);
function adaptation () {
    var w = document.body.clientWidth;
    var h = document.body.clientHeight;
    var nw = 1920;
            nh = 1080;
    var left, top, scale;
    if (w/ h > nw/ nh) {
        scale = h/ nh;
        top = 0;
        left = (w - nw * scale)/ 2;
    } else {
        scale = w/ nw;
        left = 0;
        top = (h - nh * scale)/ 2;
    }
    document.getElementById('main').setAttribute('style', 'transform: scale('+ scale +');left:'+left+'px;top:'+top+'px;');
}