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* @license Apache-2.0
*
* Copyright (c) 2021 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 isString = require( '@stdlib/assert/is-string' ).isPrimitive;
var splitGraphemeClusters = require( '@stdlib/string/split-grapheme-clusters' );
var isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive;
var isStringArray = require( '@stdlib/assert/is-string-array' ).primitives;
var replace = require( '@stdlib/string/replace' );
var rescape = require( '@stdlib/utils/escape-regexp-string' );
var format = require( '@stdlib/string/format' );
// VARIABLES //
var WHITESPACE_CHARS = '\u0020\f\n\r\t\v\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff';
// MAIN //
/**
* Trims `n` characters from the beginning of a string.
*
* @param {string} str - input string
* @param {NonNegativeInteger} n - number of characters to trim
* @param {(string|StringArray)} [chars] - characters to trim (defaults to whitespace characters)
* @throws {TypeError} first argument must be a string
* @throws {TypeError} second argument must be a nonnegative integer
* @throws {TypeError} third argument must be a string or an array of strings
* @returns {string} trimmed string
*
* @example
* var str = ' abc ';
* var out = ltrimN( str, 2 );
* // returns ' abc '
*
* @example
* var str = ' abc ';
* var out = ltrimN( str, str.length );
* // returns 'abc '
*
* @example
* var str = '~~abc!~~';
* var out = ltrimN( str, str.length, [ '~', '!' ] );
* // returns 'abc!~~'
*
* @example
* var str = '🤖👨🏼🎨🤖👨🏼🎨🤖👨🏼🎨';
* var out = ltrimN( str, str.length, '👨🏼🎨🤖' );
* // returns ''
*/
function ltrimN( str, n, chars ) {
var nElems;
var reStr;
var isStr;
var RE;
var i;
if ( !isString( str ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a string. Value: `%s`.', str ) );
}
if ( !isNonNegativeInteger( n ) ) {
throw new TypeError( format( 'invalid argument. Second argument must be a nonnegative integer. Value: `%s`.', n ) );
}
if ( arguments.length > 2 ) {
isStr = isString( chars );
if ( !isStr && !isStringArray( chars ) ) {
throw new TypeError( format( 'invalid argument. Third argument must be a string or an array of strings. Value: `%s`.', chars ) );
}
if ( isStr ) {
chars = splitGraphemeClusters( chars );
}
nElems = chars.length - 1;
reStr = '';
for ( i = 0; i < nElems; i++ ) {
reStr += rescape( chars[ i ] );
reStr += '|';
}
reStr += rescape( chars[ nElems ] );
// Case: Trim a specific set of characters from the beginning of a string..
RE = new RegExp( '^(?:' + reStr + '){0,'+n+'}' );
} else {
// Case: Trim `n` whitespace characters from the beginning of a string...
RE = new RegExp( '^[' + WHITESPACE_CHARS + ']{0,'+n+'}' );
}
return replace( str, RE, '' );
}
// EXPORTS //
module.exports = ltrimN;
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