Three common ways to automatically jump to an HTML page after 3 seconds

In practice, we often encounter a problem: how to automatically jump to the page after N seconds?
I encountered problems and searched for information, and summarized 3 methods
Method 1:
The simplest one: add code directly in the front :

<span style="font-size:18px;"> </span><span style="font-size:24px;"><meta http-equiv="refresh" content="3;URL=res.html"> </span> 
<span style="font-size:24px;">//3秒之后自动跳转到res.html，两个属于同一文件下面，要是需要跳转到jsp页面，就需要在url里面填写url地址————（浏览器的地址栏里面写入的数据，如：http://localhost:8080/TestDemo/1.jsp）</span>

Method 2:
You need to use the method in window:
setTimeout calculates an expression after specifying the millisecond value.
Example:

window.setTimeout("alert('Hello, world')", 1000);

This is written in js code;
The specific implementation is as follows:

<script type="text/javascript"> 
onload=function(){ <span style="white-space:pre"> </span>//在进入网页的时候加载该方法 
setTimeout(go, 3000); <span style="white-space:pre"> </span> /*在js中是ms的单位*/ 
}; 
function go(){ 
location.href="http://localhost:8080/TestDemo/index.jsp"; 
} 
</script> 
//3秒之后自动执行go方法，直接跳转到index.jsp页面

Method 3:
The flaw of the above two examples is that they can realize the jump, but they don’t know when to jump. Implement the countdown 3-2-1;
settimeout The method can no longer be used;
setInterval calculates an expression after each specified millisecond value.
If the same time has not passed, the corresponding function will be executed. Specific implementation methods:

<script type="text/javascript"> 
onload=function(){ 
setInterval(go, 1000); 
}; 
var x=3; //利用了全局变量来执行 
function go(){ 
x--; 
if(x>0){ 
document.getElementById("sp").innerHTML=x; //每次设置的x的值都不一样了。 
}else{ 
location.href=&#39;res.html&#39;; 
} 
} 
</script>

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