JS window.print() 調用前后監聽

var beforePrint = function(){
    console.log('beforePrint')
　　//頁面打印縮放比例設置
 document.getElementsByTagName('body')[0].style.zoom=0.92;
};

var afterPrint = function(){
    console.log('afterPrint')
   //頁面打印結束或取消時還原
 document.getElementsByTagName('body')[0].style.zoom=1;
}
if(window.matchMedia){
    var mediaQueryList = window.matchMedia('print');
    mediaQueryList.addListener(function(mql){
        if(mql.matches){
            beforePrint()
        }else{
            afterPrint();
        }
    });
}