Working with Unicode in JavaScript: A Comprehensive Guide

In this article, we will explore how to effectively work with Unicode in JavaScript. We will cover topics such as Unicode encoding of source files, how JavaScript uses Unicode internally, using Unicode characters in a string, normalization, emojis, getting the proper length of a string, ES6 Unicode code point escapes, and encoding ASCII characters.

Unicode Encoding of Source Files

When working with JavaScript, it’s important to specify the Unicode encoding of your source files, especially if you plan to use non-ASCII characters. The most common Unicode encoding for web files is UTF-8. You can specify the encoding in three ways:

Use a BOM (byte-order mark) character at the beginning of the file. However, this is not recommended for UTF-8 files.
Set the Content-Type header to application/javascript; charset=utf-8.
Add the charset attribute to the <script> tag or use the <meta charset="utf-8"> tag in the HTML document.

How JavaScript Uses Unicode Internally

JavaScript internally converts source files to UTF-16 encoding before executing them. This means that all JavaScript strings are represented as sequences of UTF-16 code units.

Using Unicode in a String

To include Unicode characters in a string, use the \uXXXX format, where XXXX represents the Unicode code point of the character. You can also combine multiple Unicode sequences to create a desired character.

Normalization

Unicode normalization is the process of resolving ambiguities in character representation to facilitate string comparison. JavaScript provides the normalize() method to perform Unicode normalization.

Emojis

Emojis are valid Unicode characters and can be used in JavaScript strings. However, some emojis are outside the Basic Multilingual Plane (BMP) and require a combination of two characters (surrogate pair) to represent them. Combining emojis together can result in different lengths, so be aware of this when working with emojis.

Getting the Proper Length of a String

The length property of a JavaScript string returns the number of Unicode code points in the string, which may not accurately represent the visual length of the string. To get the proper length, you can use the spread operator ([...'string']) or a library like Punycode.js.

ES6 Unicode Code Point Escapes

ES6 introduced a new syntax for representing Unicode code points in the astral planes using curly braces (\u{XXXXX}). This allows you to directly represent Unicode characters without combining surrogate pairs. However, be aware that length calculation still converts these code points into surrogate pairs internally.

Encoding ASCII Characters

For ASCII characters (U+0000 to U+007F), you can use the special escaping character \x followed by two hexadecimal digits to encode them.

In conclusion, working with Unicode in JavaScript requires understanding how Unicode is encoded, how JavaScript handles it internally, and how to handle Unicode characters effectively in strings. By following these practices, you can avoid unexpected issues and leverage the full power of Unicode in your JavaScript applications.

tags: [“JavaScript”, “Unicode”, “Emojis”, “ES6”, “UTF-8”, “Surrogate Pair”, “String Length”]