<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<input type = "text" id="clock" style="width: 449px" value="点击右侧[begin]按钮开始">
<input type = button value="begin" onclick="begin_click()">
<input type = button value="End" onclick="End()">
<script>
function begin() {
var stime = Date();
var ret = document.getElementById("clock");
ret.value = stime;
}
var ID;
function begin_click() {
begin()
clearInterval(ID)
ID = setInterval(begin,1000)
}
function End() {
clearInterval(ID);
}
</script>
</body>
</html>
知识点1：begin_click 里面放个 begin 即时刷新出来当前事件。
知识点2：begin_click 里面放个 clearInterval(ID) 即时结束上个id。