API / Js / Re

Re

Provide bindings to JS regular expressions (RegExp).

Note: This is not an immutable API. A RegExp object with the global ("g") flag set will modify the lastIndex property when the RegExp object is used, and subsequent uses will continue the search from the previous lastIndex.

t

RESCRIPT

type t

The RegExp object.

result

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type result

The result of a executing a RegExp on a string.

captures

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let captures: result => array<Js.nullable<string>>

An array of the match and captures, the first is the full match and the remaining are the substring captures.

matches

Deprecated

Use Js.Re.captures instead

RESCRIPT

let matches: result => array<string>

index

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let index: result => int

0-based index of the match in the input string.

input

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let input: result => string

The original input string.

fromString

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let fromString: string => t

Constructs a RegExp object (Js.Re.t) from a string. Regex literals %re("/.../") should generally be preferred, but fromString is useful when you need to dynamically construct a regex using strings, exactly like when you do so in JavaScript.

Examples

RESCRIPT
let firstReScriptFileExtension = (filename, content) => {
  let result = Js.Re.fromString(filename ++ "\.(res|resi)")->Js.Re.exec_(content)
  switch result {
  | Some(r) => Js.Nullable.toOption(Js.Re.captures(r)[1])
  | None => None
  }
}

// outputs "res"
firstReScriptFileExtension("School", "School.res School.resi Main.js School.bs.js")

fromStringWithFlags

RESCRIPT

let fromStringWithFlags: (string, ~flags: string) => t

Constructs a RegExp object (Js.Re.t) from a string with the given flags. See Js.Re.fromString.

Valid flags:

g global
i ignore case
m multiline
u unicode (es2015)
y sticky (es2015)

flags

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let flags: t => string

Returns the enabled flags as a string.

global

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let global: t => bool

Returns a bool indicating whether the global flag is set.

ignoreCase

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let ignoreCase: t => bool

Returns a bool indicating whether the ignoreCase flag is set.

lastIndex

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let lastIndex: t => int

Returns the index where the next match will start its search. This property will be modified when the RegExp object is used, if the global ("g") flag is set.

Examples

RESCRIPT
let re = %re("/ab*TODO/g")
let str = "abbcdefabh"

let break = ref(false)
while !break.contents {
  switch Js.Re.exec_(re, str) {
  | Some(result) => Js.Nullable.iter(Js.Re.captures(result)[0], (. match_) => {
      let next = Belt.Int.toString(Js.Re.lastIndex(re))
      Js.log("Found " ++ (match_ ++ (". Next match starts at " ++ next)))
    })
  | None => break := true
  }
}

See RegExp: lastIndex on MDN.

setLastIndex

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let setLastIndex: (t, int) => unit

Sets the index at which the next match will start its search from.

multiline

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let multiline: t => bool

Returns a bool indicating whether the multiline flag is set.

source

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let source: t => string

Returns the pattern as a string.

sticky

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let sticky: t => bool

Returns a bool indicating whether the sticky flag is set.

unicode

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let unicode: t => bool

Returns a bool indicating whether the unicode flag is set.

exec_

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let exec_: (t, string) => option<result>

Executes a search on a given string using the given RegExp object. Returns Some(Js.Re.result) if a match is found, None otherwise.

Examples

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/* Match "quick brown" followed by "jumps", ignoring characters in between
 * Remember "brown" and "jumps"
  * Ignore case
  */

let re = %re("/quick\s(brown).+?(jumps)/ig")
let result = Js.Re.exec_(re, "The Quick Brown Fox Jumps Over The Lazy Dog")

See RegExp.prototype.exec() on MDN.

test_

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let test_: (t, string) => bool

Tests whether the given RegExp object will match a given string. Returns true if a match is found, false otherwise.

Examples

RESCRIPT
/* A simple implementation of Js.String.startsWith */

let str = "hello world!"

let startsWith = (target, substring) =>
  Js.Re.fromString("^" ++ substring)->Js.Re.test_(target)

Js.log(str->startsWith("hello")) /* prints "true" */

See RegExp.prototype.test() on MDN.