输入密码强度验证（正则练习）
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<input type="text" id="txt"><span>弱</span><span>中</span><span>强</span>
<script>
var txt=document.getElementById("txt");
var spans=document.getElementsByTagName("span");
txt.onkeyup=function(){
var v=this.value;
var qd=0;
if(/\d/.test(v)){
qd++;
}
if(/[a-zA-Z]/.test(v)){
qd++;
}
if(/[-_]/.test(v)){
qd++;
}
if(qd==1){
spans[0].style.background="red";
spans[1].style.background="#fff";
spans[2].style.background="#fff";
}
else if(qd==2){
spans[0].style.background="#fff";
spans[1].style.background="khaki";
spans[2].style.background="#fff";
}
else if(qd==3){
spans[0].style.background="#fff";
spans[1].style.background="#fff";
spans[2].style.background="green";
}
else{
spans[0].style.background="#fff";
spans[1].style.background="#fff";
spans[2].style.background="#fff";
}
}
</script>
</body>
</html>
