Pads the current string from the start with a given string and returns a new string Pads the current string from the end with a given string and returns a new string of Returns the Unicode Normalization Form of the calling string value. Returns an iterator of all regexp's matches. Used to match regular expression regexp against a string. Returns a number indicating whether the reference stringĬompareString comes before, after, or is equivalent to the Returns the index within the calling String object of the last Returns a boolean indicating whether this string contains any lone surrogates. Occurrence of searchValue, or -1 if not found. Returns the index within the calling String object of the first ()ĭetermines whether a string ends with the characters of the stringĭetermines whether the calling string contains searchString. Returns a nonnegative integer Number that is the code point value of the UTF-16Įncoded code point starting at the specified pos.Ĭombines the text of two (or more) strings and returns a new string. Returns a number that is the UTF-16 code unit value at the given Returns the character (exactly one UTF-16 code unit) at the specified Accepts negative integers, which count back from the last string character. Returns the character (exactly one UTF-16 code unit) at the specified index. Iterating through grapheme clusters will require some custom code. On the other hand, iterates by Unicode code points. String indexes also refer to the index of each UTF-16 code unit. For example, split("") will split by UTF-16 code units and will separate surrogate pairs. You must be careful which level of characters you are iterating on. The most common case is emojis: many emojis that have a range of variations are actually formed by multiple emojis, usually joined by the ( U+200D) character. On top of Unicode characters, there are certain sequences of Unicode characters that should be treated as one visual unit, known as a grapheme cluster. You can check if a string is well-formed with the isWellFormed() method, or sanitize lone surrogates with the toWellFormed() method. Strings not containing any lone surrogates are called well-formed strings, and are safe to be used with functions that do not deal with UTF-16 (such as encodeURI() or TextEncoder). Although most JavaScript built-in methods handle them correctly because they all work based on UTF-16 code units, lone surrogates are often not valid values when interacting with other systems - for example, encodeURI() will throw a URIError for lone surrogates, because URI encoding uses UTF-8 encoding, which does not have any encoding for lone surrogates. Lone surrogates do not represent any Unicode character. is a low surrogate), but it is the first code unit in the string, or the previous code unit is not a high surrogate.
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