stdlib-js / string-for-each

Invoke a callback for each (visual) character of a string.

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forEach

Invokes a function for each character in a string.

Installation

npm install @stdlib/string-for-each

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var forEach = require( '@stdlib/string-for-each' );

forEach( str, [options,] clbk[, thisArg ] )

Invokes a function for each character in a string.

function log( value, index ) {
    console.log( '%d: %s', index, value );
}

forEach( 'Beep!', log );
/* =>
    0: B
    1: e
    2: e
    3: p
    4: !
*/

The invoked function is provided three arguments:

• value: character.
• index: starting character index.
• str: input string.

To set the function execution context, provide a thisArg.

function clbk() {
    this.count += 1;
}

var str = 'Hello, world!';

var ctx = {
    'count': 0
};

forEach( str, clbk, ctx );

var bool = ( str.length === ctx.count );
// returns true

The function supports the following options:

• mode: type of characters over which to iterate. Must be one of the following:

  • 'grapheme': grapheme clusters. Appropriate for strings containing visual characters which can span multiple Unicode code points (e.g., emoji).
  • 'code_point': Unicode code points. Appropriate for strings containing visual characters which are comprised of more than one Unicode code unit (e.g., ideographic symbols and punctuation and mathematical alphanumerics).
  • 'code_unit': UTF-16 code units. Appropriate for strings containing visual characters drawn from the basic multilingual plane (BMP) (e.g., common characters, such as those from the Latin, Greek, and Cyrillic alphabets).

  Default: 'grapheme'.

Notes

• By default, the function assumes the general case in which an input string may contain an arbitrary number of grapheme clusters. This assumption comes with a performance cost. Accordingly, if an input string is known to only contain visual characters of a particular type (e.g., only alphanumeric), one can achieve better performance by specifying the appropriate mode option.

Examples

var forEach = require( '@stdlib/string-for-each' );

function log( value, index ) {
    console.log( '%d: %s', index, value );
}

forEach( 'presidential election', log );
forEach( 'Iñtërnâtiônàlizætiøn', log );
forEach( '🌷🍕', log );
forEach( '\uD834\uDD1E', log );

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See Also

• @stdlib/utils-for-each: invoke a function for each element in a collection.

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Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.