JavaScript determines whether it is English

1. Preface

Since JavaScript is a widely used programming language for web development, server-side development, mobile application development, etc., sometimes it is necessary to determine whether a string is in English. to facilitate subsequent processing.

This article will introduce several commonly used JavaScript methods to determine whether it is English, covering regular expressions, Unicode encoding, language detection libraries and other aspects to help developers quickly determine English.

2. Regular expression to determine whether it is English

Regular expression is a method of describing character sequences, which can easily achieve string matching operations. To determine whether a string is English, we can achieve it through regular expression matching.

The following are some commonly used regular expression examples:

1. Determine whether a string consists entirely of English letters

function isEnglish(str) {
  return /^[a-zA-Z]+$/.test(str);
}

The meaning of this regular expression Yes: The string must consist entirely of letters a-z or A-Z, otherwise false is returned.

2. Determine whether the string contains English letters

function containsEnglish(str) {
  return /[a-zA-Z]/.test(str);
}

The meaning of this regular expression is: if the string contains letters a-z or A-Z, then return true, otherwise Return false.

3. Determine whether the string starts with an English letter

function startsWithEnglish(str) {
  return /^[a-zA-Z]/.test(str);
}

The meaning of this regular expression is: if the string starts with a-z or A-Z letters, it returns true, otherwise Return false.

3. Unicode encoding to determine whether it is English

Unicode is an international standard character set that covers most characters in the world. Each character has a unique encoding value in Unicode, and we can use the encoding value to determine whether the character is an English character.

The following are some commonly used Unicode encoding values:

1. Uppercase letters A～Z: 65～90
2. Lowercase letters a～z: 97～122
3. Numbers 0~9: 48~57

We can obtain the Unicode encoding value of a character through JavaScript's charCodeAt() function to determine whether it is an English character.

The following is an example:

function isEnglish(str) {
  for (var i = 0; i < str.length; i++) {
    var code = str.charCodeAt(i);
    if (code < 65 || code > 122 || (code > 90 && code < 97)) {
      return false;
    }
  }
  return true;
}

The meaning of this function is: traverse each character in the string and determine whether its Unicode encoding value is between 65~90 or 97~122 , if not within this range, return false; if all are within this range, return true.

4. Use the language detection library to determine whether it is English

The language detection library is a tool that can determine the language type of a string through a language model. If the language type of a string is English, then we can determine that it is an English string.

The following are some commonly used language detection libraries:

1. langdetect: https://github.com/wooorm/langdetect
2. franc: https://github .com/wooorm/franc
3. cld3：https://github.com/google/cld3

The following uses franc as an example to introduce how to use the language detection library to determine whether it is English:

First, we need to install the franc library:

npm install franc --save

Next, we need to introduce the franc library:

var franc = require('franc');

Then, we can use the franc.detect() function to Determine the language type of a string:

function isEnglish(str) {
  return franc(str) === 'eng';
}

The meaning of this function is: use the franc.detect() function to determine the language type of a string, if the language type is English (that is, the return value is 'eng') , returns true; otherwise returns false.

5. Summary

This article introduces a variety of JavaScript methods to determine whether it is English, including regular expressions, Unicode encoding, language detection libraries and other aspects. Developers can choose the appropriate method for implementation based on specific needs.

It should be noted that the above methods are only based on some simple rules to determine whether a string is English and cannot fully guarantee accuracy. If more precise language judgment is required, more complex language detection algorithms and models can be used.

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