Share practical cases and advanced techniques: Advanced applications of JavaScript regular expressions

Advanced application skills and practical case sharing of JavaScript regular expressions

Introduction:
Regular expression is a powerful text processing tool that is widely used in in various programming languages. In JavaScript, regular expressions also play an important role and are widely used in daily development. This article will introduce in detail the advanced application skills of JavaScript regular expressions and share some practical cases to help readers better master this technology and apply it in actual development.

1. Review of basic concepts:
Before learning JavaScript regular expressions in depth, we should first review the basic concepts of regular expressions. A regular expression is a pattern used to match, find, and replace strings. It consists of various characters and metacharacters that can be used to describe a text pattern. In JavaScript, we can use the RegExp object to create and manipulate regular expressions.

2. Advanced application skills:

1. Modifiers of regular expressions:
   In JavaScript regular expressions, modifiers modify or configure the regular expression. options. Common modifiers include i, g, m and s, etc., which respectively indicate ignoring case, global matching, multi-line matching and dot matching of any character (including newline characters), etc.

Example:

// 忽略大小写匹配
let regex = /hello/i;
console.log(regex.test("Hello")); // true

// 全局匹配
let regex2 = /hello/g;
console.log("hello world".replace(regex2, "hi")); // hi world

// 多行匹配
let regex3 = /^hello/m;
console.log(regex3.test("hello
world")); // true

// 匹配换行符
let regex4 = /hello.world/s;
console.log(regex4.test("hello
world")); // true

2. Match delimiters and boundaries:
   In regular expressions, delimiters are used to match a group of enclosed characters, common Delimiters include square brackets ([]), parentheses (()), and curly braces ({}). Boundaries are used to limit the beginning or end of a string.

Example:

// 匹配数字
let regex = /[0-9]/;
console.log(regex.test("123")); // true

// 匹配括号内的内容
let regex2 = /((.*?))/;
let match = "Hello (world)".match(regex2);
console.log(match[1]); // world

// 匹配单词边界
let regex3 = /hello/;
console.log(regex3.test("say hello")); // true

3. Non-capturing grouping:
   In regular expressions, using capturing grouping can save the matched results for subsequent use. However, in some cases, we may only need to match but do not need to retain the result, in which case non-capturing grouping can be used.

Example:

// 捕获分组
let regex = /(d+)s+s(d+)s=/;
let match = "1 + 2 =".match(regex);
console.log(match[1]); // 1
console.log(match[2]); // 2

// 非捕获分组
let regex2 = /(?:d+)s+s(?:d+)s=/;
let match2 = "1 + 2 =".match(regex2);
console.log(match2); // null

4. Search before and after:
   Search before and after in regular expressions can match the before and after content of a string based on certain conditions. The forward search uses the positive positive delimiter (?=) and the forward negative delimiter (?!), and the post-search uses the reverse positive delimiter (?

Example:

// 前查找
let regex = /hello(?= world)/;
console.log(regex.test("hello")); // false
console.log(regex.test("hello world")); // true

// 后查找
let regex2 = /(?<=hello) world/;
console.log(regex2.test("world")); // false
console.log(regex2.test("hello world")); // true

3. Practical case sharing:

1. Email verification:
   Using regular expressions can easily verify the email format. , ensure that the email format entered by the user is correct.

Example:

function validateEmail(email) {
  let regex = /w+@w+.w+/;
  return regex.test(email);
}

console.log(validateEmail("example@mail.com")); // true
console.log(validateEmail("invalid.email")); // false

2. URL extraction:
   Through regular expression matching and capture grouping, you can easily extract all URL links from a piece of text .

Example:

function extractUrls(text) {
  let regex = /https?://[^s]+/g;
  return text.match(regex);
}

let text = "Visit my website at https://example.com or https://google.com";
console.log(extractUrls(text)); // ["https://example.com", "https://google.com"]

3. Sensitive word filtering:
   Regular expressions can be used to filter sensitive words, replace sensitive words with other characters or delete them directly.

Example:

function filterSensitiveWords(text, wordList) {
  let regex = new RegExp(wordList.join('|'), 'gi');
  return text.replace(regex, '***');
}

let text = "This is a sensitive word: bad";
let wordList = ["bad"];
console.log(filterSensitiveWords(text, wordList)); // "This is a sensitive word: ***"

Summary:
This article introduces advanced application skills of JavaScript regular expressions and shares some practical cases. By learning these techniques and examples, readers can better apply regular expressions to process text content and exert powerful functions in actual development. However, regular expressions are still a complex technology, and readers should pay attention to syntactic correctness and performance considerations when using them.

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