<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>判断数字是否为两位数</title>
<style type="text/css">
body {font: 12px/1.5 arial;text-align: center;}
.f-text {width: 50px;border: 1px solid #ccc;background: #f0f0f0;font-family: inherit;padding: 3px;margin-right: 10px;}
</style>
<script type="text/javascript">
window.onload = function() {
var aInput = document.getElementsByTagName("input");
var aSpan = document.getElementsByTagName("span")[0];
var i = 0;
aInput[0].onkeyup = function() {
this.value = this.value.replace(/[^\d]/,"");
}
aInput[1].onclick = function() {
(aInput[0].value == "") ?
alert("请输入数字！") :
alert(/^\d{2}$/.test(parseInt(aInput[0].value)) ? "√ 是两位数" : "这是" + aInput[0].value.length + "位数");
}
};
</script>
</head>
<body>
<input type="text" class="f-text" /><input type="button" value="是 否为两位数" />
</body>
</html>
1.this.value = this.value.replace(/1/,"") mean?
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
[^d]represents a character that is not a number, wheredrepresents any number from0-9`,[^...]represents the inversion of the character setTherefore,
this.value.replace(/[^d]/,"")means that if the first character of the string is a number, keep it; if it is not a number, delete itFor example, the first character of
2asdand3adfis a number and will not be replaced; the first character ofsadfanda123is not a number and will be replaced by the empty string "" , that is, delete the character""means empty. replace means replacement;[^d]means non-digit (^means non, meaning not;dmeans number)means that when you type (every time you tap the keyboard), a keyboard event will be triggered. If the input is not a number (
[^d]means non-number, so use[^d]to determine whether it is a number), then replace it. (.replace means replacement) is empty (""), so if you enter something other than a number, it will be replaced immediately and will not be displayed.