The ? symbol, which is U 1F436, is traditionally encoded as \uD83D\uDC36 (called surrogate pair). normalize () //true EmojisĮmojis are fun, and they are Unicode characters, and as such they are perfectly valid to be used in strings: const s4 = '?'Įmojis are part of the astral planes, outside of the first Basic Multilingual Plane (BMP), and since those points outside BMP cannot be represented in 16 bits, JavaScript needs to use a combination of 2 characters to represent them Like in the example above: const s1 = ' \u00E9 ' //é const s3 = 'e \u0301 ' //é s1 != s3ĮS6/ES2015 introduced the normalize() method on the String prototype, so we can do: s1. Unicode normalization is the process of removing ambiguities in how a character can be represented, to aid in comparing strings, for example. length = 2 //true s2 = s3 //true s1 != s3 //true Normalization You can write a string combining a unicode character with a plain char, as internally it’s actually the same thing: const s3 = 'e \u0301 ' //é s3. length //2Īnd when you try to select that character in a text editor, you need to go through it 2 times, as the first time you press the arrow key to select it, it just selects half element. Notice that while both generate an accented e, they are two different strings, and s2 is considered to be 2 characters long: s1. Using Unicode in a stringĪ unicode sequence can be added inside any string using the format \uXXXX: const s1 = ' \u00E9 ' //éĪ sequence can be created by combining two unicode sequences: const s2 = ' \u0065\u0301 ' //é When a String contains actual textual data, each element is considered to be a single UTF-16 code unit. JavaScript strings are all UTF-16 sequences, as the ECMAScript standard says: While a JavaScript source file can have any kind of encoding, JavaScript will then convert it internally to UTF-16 before executing it. Public libraries should generally avoid using characters outside the ASCII set in their code, to avoid it being loaded by users with an encoding that is different than their original one, and thus create issues. The charset attribute in both cases is case insensitive ( see the spec)Īll this is defined in RFC 4329 “Scripting Media Types”. If this is not set, the document charset meta tag is used. If this is not set, the fallback is to check the charset attribute of the script tag: If the file is fetched using HTTP (or HTTPS), the Content-Type header can specify the encoding: Content-Type: application/javascript charset=utf-8 In HTML5 browsers are required to recognize the UTF-8 BOM and use it to detect the encoding of the page, and recent versions of major browsers handle the BOM as expected when used for UTF-8 encoded pages. … Use of a BOM is neither required nor recommended for UTF-8, but may be encountered in contexts where UTF-8 data is converted from other encoding forms that use a BOM or where the BOM is used as a UTF-8 signature. You can read many different opinions online, some say a BOM in UTF-8 is discouraged, and some editors won’t even add it. If the file contains a BOM character, that has priority on determining the encoding. How do you specify another encoding, in particular UTF-8, the most common file encoding on the web? For this reason, it’s important to set the charset of any JavaScript document. If not specified otherwise, the browser assumes the source code of any program to be written in the local charset, which varies by country and might give unexpected issues. Learn how to work with Unicode in JavaScript, learn what Emojis are made of, ES6 improvements and some pitfalls of handling Unicode in JS
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