正则表达式教程：验证帐号是否合法

一、正则解释

元字符/分组	含义
^	匹配字符串的开头
[a-zA-Z]	匹配一个字母（大小写）
\w	匹配一个字母、数字或下划线
{4,15}	匹配长度为 4-15 的字符串
$	匹配字符串的结尾

二、使用场景

该正则表达式用于验证帐号是否满足以下要求：

• 以字母开头
• 允许 5-16 个字节
• 可包含字母、数字和下划线组合

三、代码示例

JavaScript

const pattern = /^[a-zA-Z]\w{4,15}$/;
const isValid = pattern.test("justin"); // true
const isValid = pattern.test("justin1989"); // true
const isValid = pattern.test("justin_666"); // true
const isValid = pattern.test("123abc"); // false
const isValid = pattern.test("justin abc"); // false

Java

import java.util.regex.Pattern;

public class AccountValidator {

    private static final String PATTERN = "^[a-zA-Z]\\w{4,15}
import java.util.regex.Pattern;

public class AccountValidator {

    private static final String PATTERN = "^[a-zA-Z]\\w{4,15}$";

    public static boolean isValid(String account) {
        return Pattern.matches(PATTERN, account);
    }

    public static void main(String[] args) {
        System.out.println(isValid("justin")); // true
        System.out.println(isValid("justin1989")); // true
        System.out.println(isValid("justin_666")); // true
        System.out.println(isValid("123abc")); // false
        System.out.println(isValid("justin abc")); // false
    }
}
quot;;

    public static boolean isValid(String account) {
        return Pattern.matches(PATTERN, account);
    }

    public static void main(String[] args) {
        System.out.println(isValid("justin")); // true
        System.out.println(isValid("justin1989")); // true
        System.out.println(isValid("justin_666")); // true
        System.out.println(isValid("123abc")); // false
        System.out.println(isValid("justin abc")); // false
    }
}

PHP

<?php

$pattern = '/^[a-zA-Z]\w{4,15}$/';

if (preg_match($pattern, "justin")) {
    echo "Valid account";
} else {
    echo "Invalid account";
}

if (preg_match($pattern, "justin1989")) {
    echo "Valid account";
} else {
    echo "Invalid account";
}

if (preg_match($pattern, "justin_666")) {
    echo "Valid account";
} else {
    echo "Invalid account";
}

if (preg_match($pattern, "123abc")) {
    echo "Valid account";
} else {
    echo "Invalid account";
}

if (preg_match($pattern, "justin abc")) {
    echo "Valid account";
} else {
    echo "Invalid account";
}

Python

import re

pattern = r"^[a-zA-Z]\w{4,15}
import re

pattern = r"^[a-zA-Z]\w{4,15}$"

print(re.match(pattern, "justin"))  # True
print(re.match(pattern, "justin1989"))  # True
print(re.match(pattern, "justin_666"))  # True
print(re.match(pattern, "123abc"))  # None
print(re.match(pattern, "justin abc"))  # None
quot;

print(re.match(pattern, "justin"))  # True
print(re.match(pattern, "justin1989"))  # True
print(re.match(pattern, "justin_666"))  # True
print(re.match(pattern, "123abc"))  # None
print(re.match(pattern, "justin abc"))  # None