<!DOCTYPE html>
<html>
<head>
<meta charset=UTF-8>
<title>yugi</title>
<script>
onload = function(){
var btns = document.getElementsByTagName("button");
for(var i = 0; i < btns.length; i++){
btns[i].onclick = function(){
txt.value = "我是" + this.innerHTML;
}
}
}
</script>
</head>
<body>
<button>按钮1</button>
<button>按钮2</button>
<button>按钮3</button>
<input type="text" id="txt" />
</body>
</html>
追问
这段的作用是什么啊