Module Js.String

Bindings to the functions in String.prototype

JavaScript String API

type t = string;

let make: 'a => t;

make value converts the given value to a string

  make 3.5 = "3.5";;
  make [|1;2;3|]) = "1,2,3";;

let fromCharCode: int => t;

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.

  fromCharCode 65 = "A";;
  fromCharCode 0x3c8 = {js|ψ|js};;
  fromCharCode 0xd55c = {js|한|js};;
  fromCharCode -64568 = {js|ψ|js};;

let fromCharCodeMany: array(int) => t;

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

  fromCharCodeMany([|0xd55c, 0xae00, 33|]) = {js|한글!|js};;

let fromCodePoint: int => t;

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

  fromCodePoint 65 = "A";;
  fromCodePoint 0x3c8 = {js|ψ|js};;
  fromCodePoint 0xd55c = {js|한|js};;
  fromCodePoint 0x1f63a = {js|😺|js};;

let fromCodePointMany: array(int) => t;

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

  fromCodePointMany([|0xd55c; 0xae00; 0x1f63a|]) = {js|한글😺|js}

let length: t => int;

length s returns the length of the given string.

  length "abcd" = 4;;

let get: t => int => t;

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 t option.

  get "Reason" 0 = "R";;
  get "Reason" 4 = "o";;
  get {js|Rẽasöń|js} 5 = {js|ń|js};;

let charAt: index:int => t => t;

charAt ~index s gets the character at position index within string s. If index is negative or greater than the length of s, 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.

  charAt ~index:0 "Reason" = "R"
  charAt ~index:12 "Reason" = "";
  charAt ~index:5 {js|Rẽasöń|js} = {js|ń|js}

let charCodeAt: index:int => t => float;

charCodeAt s ~index returns the character code at position index 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 index is less than zero or greater than the length of the string.

  charCodeAt ~index:0 {js|😺|js} = 0xd83d
  codePointAt ~index:0 {js|😺|js} = Some 0x1f63a

let codePointAt: index:int => t => option(int);

codePointAt s ~index returns the code point at position index 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.

  codePointAt ~index:1 {js|¿😺?|js} = Some 0x1f63a
  codePointAt ~index:5 "abc" = None

ES2015

let concat: other:t => t => t;

concat ~other:str2 str1 returns a new string with str2 added after str1.

  concat ~other:"bell" "cow" = "cowbell";;

let concatMany: strings:array(t) => t => t;

concatMany ~strings original returns a new string consisting of each item of the array of strings strings added to the original string.

  concatMany ~strings:[|"2nd"; "3rd"; "4th"|] "1st" = "1st2nd3rd4th";;

let endsWith: suffix:t => ?len:int => t => bool;

endsWith ~suffix ?len str returns true if the str ends with suffix, false otherwise. If len is specified, `endsWith` only takes into account the first len characters.

  endsWith ~suffix:"cd" ~len:4 "abcd" = true;;
  endsWith ~suffix:"cd" ~len:3 "abcde" = false;;
  endsWith ~suffix:"cde" ~len:99 "abcde" = true;;
  endsWith ~suffix:"ple" ~len:7 "example.dat" = true;;
  endsWith ~suffix:"World!" "Hello, World!" = true;;
  endsWith ~suffix:"world!" "Hello, World!" = false;; (* case-sensitive *)
  endsWith ~suffix:"World" "Hello, World!" = false;; (* exact match *)

let includes: search:t => ?start:int => t => bool;

includes ~search ?start s returns true if search is found anywhere within s starting at character number start (where 0 is the first character), false otherwise.

  includes ~search:"gram" "programmer" = true;;
  includes ~search:"er" "programmer" = true;;
  includes ~search:"pro" "programmer" = true;;
  includes ~search:"xyz" "programmer" = false;;
  includes ~search:"gram" ~start:1 "programmer" = true;;
  includes ~search:"gram" ~start:4 "programmer" = false;;
  includes ~search:{js|한|js} ~start:1 {js|대한민국|js} = true;;

let indexOf: search:t => ?start:int => t => int;

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

  indexOf ~search:"ok" "bookseller" = 2;;
  indexOf ~search:"sell" "bookseller" = 4;;
  indexOf ~search:"ee" "beekeeper" = 1;;
  indexOf ~search:"xyz" "bookseller" = -1;;
  indexOf ~search:"ok" ~start:1 "bookseller" = 2;;
  indexOf ~search:"sell" ~start:2 "bookseller" = 4;;
  indexOf ~search:"sell" ~start:5 "bookseller" = -1;;

let lastIndexOf: search:t => ?start:int => t => int;

lastIndexOf ~search ~start s returns the position of the last occurrence of searchValue within s, searching backwards from the given start position. Returns -1 if searchValue is not in s. The return value is always relative to the beginning of the string.

  lastIndexOf ~search:"ok" "bookseller" = 2;;
  lastIndexOf ~search:"ee" "beekeeper" = 4;;
  lastIndexOf ~search:"xyz" "abcdefg" = -1;;
  lastIndexOf ~search:"ok" ~start:6 "bookseller" = 2;;
  lastIndexOf ~search:"ee" ~start:8 "beekeeper" = 4;;
  lastIndexOf ~search:"ee" ~start:3 "beekeeper" = 1;;
  lastIndexOf ~search:"xyz" ~start:4 "abcdefg" = -1;;

let localeCompare: other:t => t => float;

localeCompare ~other:comparison reference 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

  (localeCompare ~other:"ant" "zebra") > 0.0;;
  (localeCompare ~other:"zebra" "ant") < 0.0;;
  (localeCompare ~other:"cat" "cat") = 0.0;;
  (localeCompare ~other:"cat" "CAT") > 0.0;;

let match_: regexp:Js.re => t => option(array(option(t)));

match ~regexp str 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.

  match "The better bats" ~regexp:[%re "/b[aeiou]t/"] = Some [|"bet"|]
  match "The better bats" ~regexp:[%re "/b[aeiou]t/g"] = Some [|"bet";"bat"|]
  match "Today is 2018-04-05." ~regexp:[%re "/(\\d+)-(\\d+)-(\\d+)/"] = Some [|"2018-04-05"; "2018"; "04"; "05"|]
  match "The large container." ~regexp:[%re "/b[aeiou]g/"] = None

let normalize: ?form:[ `NFC | `NFD | `NFKC | `NFKD ] => t => t;

normalize ~form str 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. If `form` is omitted, NFC` is used.

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 https://www.unicode.org/reports/tr15/tr15-45.html Unicode technical report for details

let repeat: count:int => t => t;

repeat ~count s returns a string that consists of count repetitions of s. Raises RangeError if n is negative.

  repeat ~count:3 "ha" = "hahaha"
  repeat ~count:0 "empty" = ""

let replace: search:t => replacement:t => t => t;

replace ~search ~replacement string returns a new string which is identical to string except with the first matching instance of search replaced by replacement.

search is treated as a verbatim string to match, not a regular expression.

  replace ~search:"old" ~replacement:"new" "old string" = "new string"
  replace ~search:"the" ~replacement:"this" "the cat and the dog" = "this cat and the dog"

let replaceByRe: regexp:Js.re => replacement:t => t => t;

replaceByRe ~regexp ~replacement string returns a new string where occurrences matching regexp have been replaced by replacement.

  replaceByRe ~regexp:[%re "/[aeiou]/g"] ~replacement:"x" "vowels be gone" = "vxwxls bx gxnx"
  replaceByRe ~regexp:[%re "/(\\w+) (\\w+)/"] ~replacement:"$2, $1" "Juan Fulano" = "Fulano, Juan"

let unsafeReplaceBy0: regexp:Js.re => f:(t => int => t => t) => t => t;

unsafeReplaceBy0 ~regexp ~f s 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

let str = "beautiful vowels"
let re = [%re "/[aeiou]/g"]
let matchFn matchPart offset wholeString = Js.String.toUpperCase matchPart

let replaced = Js.String.unsafeReplaceBy0 ~regexp:re ~f:matchFn str

let () = Js.log replaced (* prints "bEAUtifUl vOwEls" *)

@see <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global\_Objects/String/replace\#Specifying\_a\_function\_as\_a\_parameter\> MDN

let unsafeReplaceBy1: regexp:Js.re => f:(t => t => int => t => t) => t => t;

unsafeReplaceBy1 ~regexp ~f s 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 strings, the offset at which the match begins, and the whole string being matched.

let str = "increment 23"
let re = [%re "/increment (\\d+)/g"]
let matchFn matchPart p1 offset wholeString =
  wholeString ^ " is " ^ (string_of_int ((int_of_string p1) + 1))

let replaced = Js.String.unsafeReplaceBy1 ~regexp:re ~f:matchFn str

let () = Js.log replaced (* prints "increment 23 is 24" *)

@see <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global\_Objects/String/replace\#Specifying\_a\_function\_as\_a\_parameter\> MDN

let unsafeReplaceBy2: 
  regexp:Js.re =>
  f:(t => t => t => int => t => t) =>
  t =>
  t;

unsafeReplaceBy2 ~regexp ~f s 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.

let str = "7 times 6"
let re = [%re "/(\\d+) times (\\d+)/"]
let matchFn matchPart p1 p2 offset wholeString =
  string_of_int ((int_of_string p1) * (int_of_string p2))

let replaced = Js.String.unsafeReplaceBy2 ~regexp:re ~f:matchFn str

let () = Js.log replaced (* prints "42" *)

see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace#Specifying_a_function_as_a_parameter MDN

let unsafeReplaceBy3: 
  regexp:Js.re =>
  f:(t => t => t => t => int => t => t) =>
  t =>
  t;

unsafeReplaceBy3 ~regexp ~f s 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 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace#Specifying_a_function_as_a_parameter MDN

let search: regexp:Js.re => t => int;

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

search ~regexp:[%re "/\\d+/"] "testing 1 2 3" = 8;;
search ~regexp:[%re "/\\d+/"] "no numbers" = -1;;

let slice: ?start:int => ?end_:int => t => t;

slice ?start ?end str returns the substring of str starting at character start up to but not including end

If either start or end is negative, then it is evaluated as length str - start (or length str - end).

If end is greater than the length of str, then it is treated as length str.

If start is greater than end, slice returns the empty string.

  slice ~start:2 ~end_:5 "abcdefg" = "cde";;
  slice ~start:2 ~end_:9 "abcdefg" = "cdefg";;
  slice ~start:(-4) ~end_:(-2) "abcdefg" = "de";;
  slice ~start:5 ~end_:1 "abcdefg" = "";;

let split: ?sep:t => ?limit:int => t => array(t);

split ?sep ?limit str splits the given str at every occurrence of sep and returns an array of the first limit resulting substrings. If limit is negative or greater than the number of substrings, the array will contain all the substrings.

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

let splitByRe: regexp:Js.re => ?limit:int => t => array(option(t));

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

  splitByRe ~regexp:[%re "/\\s*:\\s*/"] ~limit:3 "one: two: three: four" = [|"one"; "two"; "three"|];;
  splitByRe ~regexp:[%re "/\\s*:\\s*/"] ~limit:0 "one: two: three: four" = [| |];;
  splitByRe ~regexp:[%re "/\\s*:\\s*/"] ~limit:8 "one: two: three: four" = [|"one"; "two"; "three"; "four"|];;

;

let startsWith: prefix:t => ?start:int => t => bool;

startsWith ~prefix ?start str returns true if the str starts with prefix starting at position start, false otherwise. If start is negative, the search starts at the beginning of str.

  startsWith ~prefix:"Hello" ~start:0 "Hello, World!" = true;;
  startsWith ~prefix:"World" ~start:7 "Hello, World!" = true;;
  startsWith ~prefix:"World" ~start:8 "Hello, World!" = false;;

let substr: ?start:int => ?len:int => t => t;

substr ?start ?len str returns the substring of str of length len starting at position start.

If start is less than zero, the starting position is the length of str

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

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

  substr ~start:3 ~len:4 "abcdefghij" = "defghij"
  substr ~start:(-3) ~len:4 "abcdefghij" = "hij"
  substr ~start:12 ~len:2 "abcdefghij" = ""

deprecated This function is deprecated, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global\_Objects/String/substr\#sect1

let substring: ?start:int => ?end_:int => t => t;

substring ~start ~end_ str returns characters start up to but not including end_ from str.

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

If end_ is zero or negative, the empty string is returned.

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

  substring ~start:3 ~end_:6 "playground" = "ygr";;
  substring ~start:6 ~end_:3 "playground" = "ygr";;
  substring ~start:4 ~end_:12 "playground" = "ground";;

let toLowerCase: t => t;

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 when it is the last character in a string or not.

  toLowerCase "ABC" = "abc";;
  toLowerCase {js|ΣΠ|js} = {js|σπ|js};;
  toLowerCase {js|ΠΣ|js} = {js|πς|js};;

let toLocaleLowerCase: t => t;

toLocaleLowerCase str converts str to lower case using the current locale

let toUpperCase: t => t;

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.

  toUpperCase "abc" = "ABC";;
  toUpperCase {js|Straße|js} = {js|STRASSE|js};;
  toUpperCase {js|πς|js} = {js|ΠΣ|js};;

let toLocaleUpperCase: t => t;

toLocaleUpperCase str converts str to upper case using the current locale

let trim: t => t;

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

  trim "   abc def   " = "abc def"
  trim "\n\r\t abc def \n\n\t\r " = "abc def"

let anchor: name:t => t => t;

anchor ~name:anchorName anchorText creates a string with an HTML <a> element with name attribute of anchorName and anchorText as its content.

  anchor ~name:"page1" "Page One" = "<a name=\"page1\">Page One</a>"

deprecated This function is deprecated, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global\_Objects/String/anchor\#sect1

let link: href:t => t => t;

link ~href:urlText linkText creates a string with an HTML <a> element with href attribute of urlText and linkText as its content.

  link ~href:"page2.html" "Go to page two" = "<a href=\"page2.html\">Go to page two</a>"

deprecated This function is deprecated, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global\_Objects/String/link\#sect1

let unsafeToArrayLike: t => Js.array_like(t);