4.窗口有关

4-1 onresize 窗口大小改变的时候触发

window.onresize = function(){
  console.log("窗口大小改变了");
}

4-2 onscroll 窗口滚动时触发

window.onscroll = function(){
  console.log(2);
}

4-3 onload 页面在加载完毕之后才会触发

<p id="p">hello world</p>
window.onload = function(){
  var p = document.getElementById("p")
  p.onclick = function(){
    console.log("hello world");
  }
}