@stdlib/string/base/first-grapheme-cluster/lib/main.js

String manipulation functions.

/**
* @license Apache-2.0
*
* Copyright (c) 2023 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*    http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

'use strict';

// MODULES //

var nextGraphemeClusterBreak = require( './../../../next-grapheme-cluster-break' );


// MAIN //

/**
* Returns the first `n` grapheme clusters (i.e., user-perceived characters) of a string.
*
* @param {string} str - input string
* @param {NonNegativeInteger} n - number of grapheme clusters to return
* @returns {string} output string
*
* @example
* var out = first( 'last man standing', 1 );
* // returns 'l'
*
* @example
* var out = first( 'presidential election', 1 );
* // returns 'p'
*
* @example
* var out = first( 'JavaScript', 1 );
* // returns 'J'
*
* @example
* var out = first( 'Hidden Treasures', 1 );
* // returns 'H'
*
* @example
* var out = first( '🐶🐮🐷🐰🐸', 2 );
* // returns '🐶🐮'
*
* @example
* var out = first( 'foo bar', 5 );
* // returns 'foo b'
*/
function first( str, n ) {
	var i = 0;
	while ( n > 0 ) {
		i = nextGraphemeClusterBreak( str, i );
		n -= 1;
	}
	// Value of `i` will be -1 if and only if `str` is an empty string or `str` has only 1 extended grapheme cluster...
	if ( str === '' || i === -1 ) {
		return str;
	}
	return str.substring( 0, i );
}


// EXPORTS //

module.exports = first;