console 命令行工具 X clear

console

var button = document.getElementById('button');
console.log(button);
button.onmousedown = function(e){
  console.log(e);
}

button.onmouseup = function(e){
  console.log(e);
}

button.onclick = function(){
  console.log(123)
}

<button id="button">按钮</button>