javascript 得到当前页面可视高度和宽度

function getHeight(){
    var yScroll;
    if (window.innerHeight && window.scrollMaxY) {
        yScroll = window.innerHeight + window.scrollMaxY;
    } else if (document.body.scrollHeight > document.body.offsetHeight){ // all but Explorer Mac
        yScroll = document.body.scrollHeight;
    } else { // Explorer Mac...would also work in Explorer 6 Strict, Mozilla and Safari
        yScroll = document.body.offsetHeight;
    }
  
    var windowHeight;
    if (self.innerHeight) { // all except Explorer
        windowHeight = self.innerHeight;
    } else if (document.documentElement && document.documentElement.clientHeight) {
    // Explorer 6 Strict Mode
       windowHeight = document.documentElement.clientHeight;
    } else if (document.body) { // other Explorers
       windowHeight = document.body.clientHeight;
    }
    // for small pages with total height less then height of the viewport
    if(yScroll < windowHeight){
        pageHeight = windowHeight;
    } else {
        pageHeight = yScroll;
    }
      return pageHeight;
}
         
function getWidth(){
        var xScroll
        if (window.innerHeight && window.scrollMaxY) {
        xScroll = document.body.scrollWidth;
        } else if (document.body.scrollHeight > document.body.offsetHeight){ // all b