API / Js / Js_string2

Js_string2

Provide bindings to JS string. Optimized for pipe-first.

t

type t = string

make

make(value) converts the given value to a string.

RES
Js.String2.make(3.5) == "3.5"
Js.String2.make([1, 2, 3]) == "1,2,3"

let make: 'a => t

fromCharCode

fromCharCode(n) creates a string containing the character corresponding to that number; n ranges from 0 to 65535.If out of range, the lower 16 bits of the value are used. Thus, fromCharCode(0x1F63A) gives the same result as fromCharCode(0xF63A).

See String.fromCharCode on MDN.

RES
Js.String2.fromCharCode(65) == "A"
Js.String2.fromCharCode(0x3c8) == `ψ`
Js.String2.fromCharCode(0xd55c) == `한`
Js.String2.fromCharCode(-64568) == `ψ`

let fromCharCode: int => t

fromCharCodeMany

fromCharCodeMany([n1, n2, n3]) creates a string from the characters corresponding to the given numbers, using the same rules as fromCharCode.

See String.fromCharCode on MDN.

let fromCharCodeMany: array<int> => t

fromCodePoint

fromCodePoint(n) creates a string containing the character corresponding to that numeric code point. If the number is not a valid code point, it raises RangeError. Thus, fromCodePoint(0x1F63A) will produce a correct value, unlike fromCharCode(0x1F63A), and fromCodePoint(-5) will raise a RangeError.

See String.fromCodePoint on MDN.

RES
Js.String2.fromCodePoint(65) == "A"
Js.String2.fromCodePoint(0x3c8) == `ψ`
Js.String2.fromCodePoint(0xd55c) == `한`
Js.String2.fromCodePoint(0x1f63a) == `😺`

let fromCodePoint: int => t

fromCodePointMany

fromCodePointMany([n1, n2, n3]) creates a string from the characters corresponding to the given code point numbers, using the same rules as fromCodePoint.

See String.fromCodePoint on MDN.

RES
Js.String2.fromCodePointMany([0xd55c, 0xae00, 0x1f63a]) == `한글😺`

let fromCodePointMany: array<int> => t

length

length(s) returns the length of the given string.

See String.length on MDN.

RES
Js.String2.length("abcd") == 4

let length: t => int

get

get(s, n) returns as a string the character at the given index number. If n is out of range, this function returns undefined,so at some point this function may be modified to return option(string).

RES
Js.String2.get("Reason", 0) == "R"
Js.String2.get("Reason", 4) == "o"
Js.String2.get(`Rẽasöń`, 5) == `ń`

let get: (t, int) => t

charAt

charAt(s, n) gets the character at index n within string s. If n is negative or greater than the length of s, it returns the empty string. If the string contains characters outside the range \u0000-\uffff, it will return the first 16-bit value at that position in the string.

See String.charAt on MDN.

RES
Js.String2.charAt("Reason", 0) == "R"
Js.String2.charAt("Reason", 12) == ""
Js.String2.charAt(`Rẽasöń`, 5) == `ń`

let charAt: (t, int) => t

charCodeAt

charCodeAt(s, n) returns the character code at position n in string s; the result is in the range 0-65535, unlke codePointAt, so it will not work correctly for characters with code points greater than or equal to 0x10000. The return type is float because this function returns NaN if n is less than zero or greater than the length of the string.

See String.charCodeAt on MDN.

RES
Js.String2.charCodeAt(`😺`, 0) == 0xd83d->Belt.Int.toFloat
Js.String2.codePointAt(`😺`, 0) == Some(0x1f63a)

let charCodeAt: (t, int) => float

codePointAt

codePointAt(s, n) returns the code point at position n within string s as a Some(value). The return value handles code points greater than or equal to 0x10000. If there is no code point at the given position, the function returns None.

See String.codePointAt on MDN.

RES
Js.String2.codePointAt(`¿😺?`, 1) == Some(0x1f63a)
Js.String2.codePointAt("abc", 5) == None

let codePointAt: (t, int) => option<int>

concat

concat(original, append) returns a new string with append added after original.

See String.concat on MDN.

RES
Js.String2.concat("cow", "bell") == "cowbell"

let concat: (t, t) => t

concatMany

concatMany(original, arr) returns a new string consisting of each item of an array of strings added to the original string.

See String.concat on MDN.

RES
Js.String2.concatMany("1st", ["2nd", "3rd", "4th"]) == "1st2nd3rd4th"

let concatMany: (t, array<t>) => t

endsWith

ES2015: endsWith(str, substr) returns true if the str ends with substr, false otherwise.

See String.endsWith on MDN.

RES
Js.String2.endsWith("ReScript", "Script") == true
Js.String2.endsWith("C++", "Script") == false

let endsWith: (t, t) => bool

endsWithFrom

endsWithFrom(str, ending, len) returns true if the first len characters of str end with ending, false otherwise. If len is greater than or equal to the length of str, then it works like endsWith. (Honestly, this should have been named endsWithAt, but oh well).

See String.endsWith on MDN.

RES
Js.String2.endsWithFrom("abcd", "cd", 4) == true
Js.String2.endsWithFrom("abcde", "cd", 3) == false
Js.String2.endsWithFrom("abcde", "cde", 99) == true
Js.String2.endsWithFrom("example.dat", "ple", 7) == true

let endsWithFrom: (t, t, int) => bool

includes

ES2015: includes(str, searchValue) returns true if searchValue is found anywhere within str, false otherwise.

See String.includes on MDN.

RES
Js.String2.includes("programmer", "gram") == true
Js.String2.includes("programmer", "er") == true
Js.String2.includes("programmer", "pro") == true
Js.String2.includes("programmer.dat", "xyz") == false

let includes: (t, t) => bool

includesFrom

ES2015: includes(str, searchValue start) returns true if searchValue is found anywhere within str starting at character number start (where 0 is the first character), false otherwise.

See String.includes on MDN.

RES
Js.String2.includesFrom("programmer", "gram", 1) == true
Js.String2.includesFrom("programmer", "gram", 4) == false
Js.String2.includesFrom(`대한민국`, `한`, 1) == true

let includesFrom: (t, t, int) => bool

indexOf

ES2015: indexOf(str, searchValue) returns the position at which searchValue was first found within str, or -1 if searchValue is not in str.

See String.indexOf on MDN.

RES
Js.String2.indexOf("bookseller", "ok") == 2
Js.String2.indexOf("bookseller", "sell") == 4
Js.String2.indexOf("beekeeper", "ee") == 1
Js.String2.indexOf("bookseller", "xyz") == -1

let indexOf: (t, t) => int

indexOfFrom

indexOfFrom(str, searchValue, start) returns the position at which searchValue was found within str starting at character position start, or -1 if searchValue is not found in that portion of str. The return value is relative to the beginning of the string, no matter where the search started from.

See String.indexOf on MDN.

RES
Js.String2.indexOfFrom("bookseller", "ok", 1) == 2
Js.String2.indexOfFrom("bookseller", "sell", 2) == 4
Js.String2.indexOfFrom("bookseller", "sell", 5) == -1

let indexOfFrom: (t, t, int) => int

lastIndexOf

lastIndexOf(str, searchValue) returns the position of the last occurrence of searchValue within str, searching backwards from the end of the string. Returns -1 if searchValue is not in str. The return value is always relative to the beginning of the string.

See String.lastIndexOf on MDN.

RES
Js.String2.lastIndexOf("bookseller", "ok") == 2
Js.String2.lastIndexOf("beekeeper", "ee") == 4
Js.String2.lastIndexOf("abcdefg", "xyz") == -1

let lastIndexOf: (t, t) => int

lastIndexOfFrom

lastIndexOfFrom(str, searchValue, start) returns the position of the last occurrence of searchValue within str, searching backwards from the given start position. Returns -1 if searchValue is not in str. The return value is always relative to the beginning of the string.

See String.lastIndexOf on MDN.

RES
Js.String2.lastIndexOfFrom("bookseller", "ok", 6) == 2
Js.String2.lastIndexOfFrom("beekeeper", "ee", 8) == 4
Js.String2.lastIndexOfFrom("beekeeper", "ee", 3) == 1
Js.String2.lastIndexOfFrom("abcdefg", "xyz", 4) == -1

let lastIndexOfFrom: (t, t, int) => int

localeCompare

localeCompare(reference, comparison) returns

  • a negative value if reference comes before comparison in sort order

  • zero if reference and comparison have the same sort order

  • a positive value if reference comes after comparison in sort order

See String.localeCompare on MDN.

RES
Js.String2.localeCompare("zebra", "ant") > 0.0
Js.String2.localeCompare("ant", "zebra") < 0.0
Js.String2.localeCompare("cat", "cat") == 0.0
Js.String2.localeCompare("CAT", "cat") > 0.0

let localeCompare: (t, t) => float

match_

match(str, regexp) matches a string against the given regexp. If there is no match, it returns None. For regular expressions without the g modifier, if there is a match, the return value is Some(array) where the array contains:

  • The entire matched string

  • Any capture groups if the regexp had parentheses For regular expressions with the g modifier, a matched expression returns Some(array) with all the matched substrings and no capture groups.

See String.match on MDN.

RES
Js.String2.match_("The better bats", %re("/b[aeiou]t/")) == Some(["bet"])
Js.String2.match_("The better bats", %re("/b[aeiou]t/g")) == Some(["bet", "bat"])
Js.String2.match_("Today is 2018-04-05.", %re("/(\d+)-(\d+)-(\d+)/")) ==
  Some(["2018-04-05", "2018", "04", "05"])
Js.String2.match_("The large container.", %re("/b[aeiou]g/")) == None

let match_: (t, Js_re.t) => option<array<option<t>>>

normalize

normalize(str) returns the normalized Unicode string using Normalization Form Canonical (NFC) Composition. Consider the character ã, which can be represented as the single codepoint \u00e3 or the combination of a lower case letter A \u0061 and a combining tilde \u0303. Normalization ensures that both can be stored in an equivalent binary representation.

See String.normalize on MDN. See also Unicode technical report #15 for details.

let normalize: t => t

normalizeByForm

ES2015: normalize(str, form) returns the normalized Unicode string using the specified form of normalization, which may be one of:

  • "NFC" — Normalization Form Canonical Composition.

  • "NFD" — Normalization Form Canonical Decomposition.

  • "NFKC" — Normalization Form Compatibility Composition.

  • "NFKD" — Normalization Form Compatibility Decomposition.

See String.normalize on MDN. See also Unicode technical report #15 for details.

let normalizeByForm: (t, t) => t

repeat

repeat(str, n) returns a string that consists of n repetitions of str. Raises RangeError if n is negative.

See String.repeat on MDN.

RES
Js.String2.repeat("ha", 3) == "hahaha"
Js.String2.repeat("empty", 0) == ""

let repeat: (t, int) => t

replace

ES2015: replace(str, substr, newSubstr) returns a new string which is identical to str except with the first matching instance of substr replaced by newSubstr. substr is treated as a verbatim string to match, not a regular expression.

See String.replace on MDN.

RES
Js.String2.replace("old string", "old", "new") == "new string"
Js.String2.replace("the cat and the dog", "the", "this") == "this cat and the dog"

let replace: (t, t, t) => t

replaceByRe

replaceByRe(str, regex, replacement) returns a new string where occurrences matching regex have been replaced by replacement.

See String.replace on MDN.

RES
Js.String2.replaceByRe("vowels be gone", %re("/[aeiou]/g"), "x") == "vxwxls bx gxnx"
Js.String2.replaceByRe("Juan Fulano", %re("/(\w+) (\w+)/"), "$2, $1") == "Fulano, Juan"

let replaceByRe: (t, Js_re.t, t) => t

unsafeReplaceBy0

Returns a new string with some or all matches of a pattern with no capturing parentheses replaced by the value returned from the given function. The function receives as its parameters the matched string, the offset at which the match begins, and the whole string being matched.

See String.replace on MDN.

RES
let str = "beautiful vowels"
let re = %re("/[aeiou]/g")
let matchFn = (matchPart, _offset, _wholeString) => Js.String2.toUpperCase(matchPart)

Js.String2.unsafeReplaceBy0(str, re, matchFn) == "bEAUtIfUl vOwEls"

let unsafeReplaceBy0: (t, Js_re.t, (t, int, t) => t) => t

unsafeReplaceBy1

Returns a new string with some or all matches of a pattern with one set of capturing parentheses replaced by the value returned from the given function. The function receives as its parameters the matched string, the captured string, the offset at which the match begins, and the whole string being matched.

See String.replace on MDN.

RES
let str = "Jony is 40"
let re = %re("/(Jony is )\d+/g")
let matchFn = (_match, part1, _offset, _wholeString) => {
  part1 ++ "41"
}

Js.String2.unsafeReplaceBy1(str, re, matchFn) == "Jony is 41"

let unsafeReplaceBy1: (t, Js_re.t, (t, t, int, t) => t) => t

unsafeReplaceBy2

Returns a new string with some or all matches of a pattern with two sets of capturing parentheses replaced by the value returned from the given function. The function receives as its parameters the matched string, the captured strings, the offset at which the match begins, and the whole string being matched.

See String.replace on MDN.

RES
let str = "7 times 6"
let re = %re("/(\d+) times (\d+)/")
let matchFn = (_match, p1, p2, _offset, _wholeString) => {
  switch (Belt.Int.fromString(p1), Belt.Int.fromString(p2)) {
  | (Some(x), Some(y)) => Belt.Int.toString(x * y)
  | _ => "???"
  }
}

Js.String2.unsafeReplaceBy2(str, re, matchFn) == "42"

let unsafeReplaceBy2: (t, Js_re.t, (t, t, t, int, t) => t) => t

unsafeReplaceBy3

Returns a new string with some or all matches of a pattern with three sets of capturing parentheses replaced by the value returned from the given function. The function receives as its parameters the matched string, the captured strings, the offset at which the match begins, and the whole string being matched.

See String.replace on MDN.

let unsafeReplaceBy3: (t, Js_re.t, (t, t, t, t, int, t) => t) => t

search

search(str, regexp) returns the starting position of the first match of regexp in the given str, or -1 if there is no match.

See String.search on MDN.

RES
Js.String2.search("testing 1 2 3", %re("/\d+/")) == 8
Js.String2.search("no numbers", %re("/\d+/")) == -1

let search: (t, Js_re.t) => int

slice

slice(str, from:n1, to_:n2) returns the substring of str starting at character n1 up to but not including n2.

  • If either n1 or n2 is negative, then it is evaluated as length(str - n1) or length(str - n2).

  • If n2 is greater than the length of str, then it is treated as length(str).

  • If n1 is greater than n2, slice returns the empty string.

See String.slice on MDN.

RES
Js.String2.slice("abcdefg", ~from=2, ~to_=5) == "cde"
Js.String2.slice("abcdefg", ~from=2, ~to_=9) == "cdefg"
Js.String2.slice("abcdefg", ~from=-4, ~to_=-2) == "de"
Js.String2.slice("abcdefg", ~from=5, ~to_=1) == ""

let slice: (t, ~from: int, ~to_: int) => t

sliceToEnd

sliceToEnd(str, from:n) returns the substring of str starting at character n to the end of the string.

  • If n is negative, then it is evaluated as length(str - n).

  • If n is greater than the length of str, then sliceToEnd returns the empty string.

See String.slice on MDN.

RES
Js.String2.sliceToEnd("abcdefg", ~from=4) == "efg"
Js.String2.sliceToEnd("abcdefg", ~from=-2) == "fg"
Js.String2.sliceToEnd("abcdefg", ~from=7) == ""

let sliceToEnd: (t, ~from: int) => t

split

split(str, delimiter) splits the given str at every occurrence of delimiter and returns an array of the resulting substrings.

See String.split on MDN.

RES
Js.String2.split("2018-01-02", "-") == ["2018", "01", "02"]
Js.String2.split("a,b,,c", ",") == ["a", "b", "", "c"]
Js.String2.split("good::bad as great::awful", "::") == ["good", "bad as great", "awful"]
Js.String2.split("has-no-delimiter", ";") == ["has-no-delimiter"]

let split: (t, t) => array<t>

splitAtMost

splitAtMost delimiter ~limit: n str splits the given str at every occurrence of delimiter and returns an array of the first n resulting substrings. If n is negative or greater than the number of substrings, the array will contain all the substrings.

splitAtMost "ant/bee/cat/dog/elk" "/" ~limit: 3 = [|"ant"; "bee"; "cat"|];;
splitAtMost "ant/bee/cat/dog/elk" "/" ~limit: 0 = [| |];;
splitAtMost "ant/bee/cat/dog/elk" "/" ~limit: 9 = [|"ant"; "bee"; "cat"; "dog"; "elk"|];;

let splitAtMost: (t, t, ~limit: int) => array<t>

splitByRe

splitByRe(str, regex) splits the given str at every occurrence of regex and returns an array of the resulting substrings.

See String.split on MDN.

RES
Js.String2.splitByRe("art; bed , cog ;dad", %re("/\s*[,;]\s*TODO/")) == [
    Some("art"),
    Some("bed"),
    Some("cog"),
    Some("dad"),
  ]

let splitByRe: (t, Js_re.t) => array<option<t>>

splitByReAtMost

splitByReAtMost(str, regex, ~limit:n) splits the given str at every occurrence of regex and returns an array of the first n resulting substrings. If n is negative or greater than the number of substrings, the array will contain all the substrings.

See String.split on MDN.

RES
Js.String2.splitByReAtMost("one: two: three: four", %re("/\s*:\s*TODO/"), ~limit=3) == [
    Some("one"),
    Some("two"),
    Some("three"),
  ]

Js.String2.splitByReAtMost("one: two: three: four", %re("/\s*:\s*TODO/"), ~limit=0) == []

Js.String2.splitByReAtMost("one: two: three: four", %re("/\s*:\s*TODO/"), ~limit=8) == [
    Some("one"),
    Some("two"),
    Some("three"),
    Some("four"),
  ]

let splitByReAtMost: (t, Js_re.t, ~limit: int) => array<option<t>>

startsWith

ES2015: startsWith(str, substr) returns true if the str starts with substr, false otherwise.

See String.startsWith on MDN.

RES
Js.String2.startsWith("ReScript", "Re") == true
Js.String2.startsWith("ReScript", "") == true
Js.String2.startsWith("JavaScript", "Re") == false

let startsWith: (t, t) => bool

startsWithFrom

ES2015: startsWithFrom(str, substr, n) returns true if the str starts with substr starting at position n, false otherwise. If n is negative, the search starts at the beginning of str.

See String.startsWith on MDN.

RES
Js.String2.startsWithFrom("ReScript", "Scri", 2) == true
Js.String2.startsWithFrom("ReScript", "", 2) == true
Js.String2.startsWithFrom("JavaScript", "Scri", 2) == false

let startsWithFrom: (t, t, int) => bool

substr

substr(str, ~from:n) returns the substring of str from position n to the end of the string.

  • If n is less than zero, the starting position is the length of str - n.

  • If n is greater than or equal to the length of str, returns the empty string.

JavaScript’s String.substr() is a legacy function. When possible, use substring() instead.

See String.substr on MDN.

RES
Js.String2.substr("abcdefghij", ~from=3) == "defghij"
Js.String2.substr("abcdefghij", ~from=-3) == "hij"
Js.String2.substr("abcdefghij", ~from=12) == ""

let substr: (t, ~from: int) => t

substrAtMost

substrAtMost(str, ~from: pos, ~length: n) returns the substring of str of length n starting at position pos.

  • If pos is less than zero, the starting position is the length of str - pos.

  • If pos is greater than or equal to the length of str, returns the empty string.

  • If n is less than or equal to zero, returns the empty string.

JavaScript’s String.substr() is a legacy function. When possible, use substring() instead.

See String.substr on MDN.

RES
Js.String2.substrAtMost("abcdefghij", ~from=3, ~length=4) == "defg"
Js.String2.substrAtMost("abcdefghij", ~from=-3, ~length=4) == "hij"
Js.String2.substrAtMost("abcdefghij", ~from=12, ~length=2) == ""

let substrAtMost: (t, ~from: int, ~length: int) => t

substring

substring(str, ~from: start, ~to_: finish) returns characters start up to but not including finish from str.

  • If start is less than zero, it is treated as zero.

  • If finish is zero or negative, the empty string is returned.

  • If start is greater than finish, the start and finish points are swapped.

See String.substring on MDN.

RES
Js.String2.substring("playground", ~from=3, ~to_=6) == "ygr"
Js.String2.substring("playground", ~from=6, ~to_=3) == "ygr"
Js.String2.substring("playground", ~from=4, ~to_=12) == "ground"

let substring: (t, ~from: int, ~to_: int) => t

substringToEnd

substringToEnd(str, ~from: start) returns the substring of str from position start to the end.

  • If start is less than or equal to zero, the entire string is returned.

  • If start is greater than or equal to the length of str, the empty string is returned.

See String.substring on MDN.

RES
Js.String2.substringToEnd("playground", ~from=4) == "ground"
Js.String2.substringToEnd("playground", ~from=-3) == "playground"
Js.String2.substringToEnd("playground", ~from=12) == ""

let substringToEnd: (t, ~from: int) => t

toLowerCase

toLowerCase(str) converts str to lower case using the locale-insensitive case mappings in the Unicode Character Database. Notice that the conversion can give different results depending upon context, for example with the Greek letter sigma, which has two different lower case forms; one when it is the last character in a string and another when it is not.

See String.toLowerCase on MDN.

RES
Js.String2.toLowerCase("ABC") == "abc"
Js.String2.toLowerCase(`ΣΠ`) == `σπ`
Js.String2.toLowerCase(`ΠΣ`) == `πς`

let toLowerCase: t => t

toLocaleLowerCase

toLocaleLowerCase(str) converts str to lower case using the current locale. See String.toLocaleLowerCase on MDN.

let toLocaleLowerCase: t => t

toUpperCase

toUpperCase(str) converts str to upper case using the locale-insensitive case mappings in the Unicode Character Database. Notice that the conversion can expand the number of letters in the result; for example the German ß capitalizes to two Ses in a row.

See String.toUpperCase on MDN.

RES
Js.String2.toUpperCase("abc") == "ABC"
Js.String2.toUpperCase(`Straße`) == `STRASSE`
Js.String2.toUpperCase(`πς`) == `ΠΣ`

let toUpperCase: t => t

toLocaleUpperCase

toLocaleUpperCase(str) converts str to upper case using the current locale. See String.to:LocaleUpperCase on MDN.

let toLocaleUpperCase: t => t

trim

trim(str) returns a string that is str with whitespace stripped from both ends. Internal whitespace is not removed.

See String.trim on MDN.

RES
Js.String2.trim("   abc def   ") == "abc def"
Js.String2.trim("\n\r\t abc def \n\n\t\r ") == "abc def"

let trim: t => t

anchor

anchor(anchorText, anchorName) creates a string with an HTML <a> element with name attribute of anchorName and anchorText as its content. Please do not use this method, as it has been removed from the relevant web standards.

See String.anchor on MDN.

RES
Js.String2.anchor("Page One", "page1") == "<a name="page1">Page One</a>"

let anchor: (t, t) => t

link

ES2015: link(linkText, urlText) creates a string with an HTML <a> element with href attribute of urlText and linkText as its content. Please do not use this method, as it has been removed from the relevant web standards. See String.link on MDN.

RES
Js.String2.link("Go to page two", "page2.html") == "<a href="page2.html">Go to page two</a>"

let link: (t, t) => t

castToArrayLike

Casts its argument to an array_like entity that can be processed by functions such as Js.Array2.fromMap()

RES
let s = "abcde"
let arr = Js.Array2.fromMap(Js.String2.castToArrayLike(s), x => x)
arr == ["a", "b", "c", "d", "e"]

let castToArrayLike: t => Js_array2.array_like<t>