93 lines
2.5 KiB
JavaScript
93 lines
2.5 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
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var isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive;
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var nextGraphemeClusterBreak = require( './../../next-grapheme-cluster-break' );
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var format = require( './../../format' );
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// MAIN //
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/**
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* Removes the first character(s) of a string.
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*
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* @param {string} str - input string
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* @param {NonNegativeInteger} [n=1] - number of characters to remove
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* @throws {TypeError} must provide a string primitive
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* @throws {TypeError} second argument must be a nonnegative integer
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* @returns {string} updated string
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*
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* @example
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* var out = removeFirst( 'last man standing' );
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* // returns 'ast man standing'
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*
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* @example
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* var out = removeFirst( 'presidential election' );
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* // returns 'residential election'
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*
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* @example
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* var out = removeFirst( 'javaScript' );
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* // returns 'avaScript'
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*
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* @example
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* var out = removeFirst( 'Hidden Treasures' );
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* // returns 'idden Treasures'
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*
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* @example
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* var out = removeFirst( '🐶🐮🐷🐰🐸', 2 );
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* // returns '🐷🐰🐸'
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*
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* @example
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* var out = removeFirst( 'foo bar', 4 );
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* // returns 'bar'
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*/
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function removeFirst( str, n ) {
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var nextBreak;
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if ( !isString( str ) ) {
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throw new TypeError( format( 'invalid argument. First argument must be a string. Value: `%s`.', str ) );
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}
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if ( arguments.length > 1 ) {
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if ( !isNonNegativeInteger( n ) ) {
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throw new TypeError( format( 'invalid argument. Second argument must be a nonnegative integer. Value: `%s`.', n ) );
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}
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nextBreak = 0;
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while ( n > 0 ) {
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nextBreak = nextGraphemeClusterBreak( str, nextBreak );
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n -= 1;
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}
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}
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else {
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nextBreak = nextGraphemeClusterBreak( str );
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}
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// Value of `nextBreak` will be -1 if and only if `str` is an empty string or `str` has only 1 extended grapheme cluster...
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if ( str === '' || nextBreak === -1 ) {
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return '';
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}
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return str.substring( nextBreak );
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}
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// EXPORTS //
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module.exports = removeFirst;
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