行内绑定
//只执行fun1();
<button onclick="fun1()" onclick="fun2()">按钮</button>
//两个都执行;
<button onclick="fun1();fun2()">按钮</button>
onclick属性
//只执行第二个函数;
var button = document.getElementsByTagName("button")[0];
button.onclick = function(){
console.log(1);
}
button.onclick = function(){
console.log(2);
}
addEventListener方法
//两个都执行;
var button = document.getElementsByTagName("button")[0];
button.addEventListener('click',fun1);
button.addEventListener('click',fun2);