73 lines
1.8 KiB
JavaScript
73 lines
1.8 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2021 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 format = require( './../../format' );
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// MAIN //
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/**
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* Returns the part of a string before a specified substring.
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*
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* @param {string} str - input string
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* @param {string} search - search string
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* @throws {TypeError} first argument must be a string
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* @throws {TypeError} second argument must be a string
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* @returns {string} substring
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*
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* @example
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* var out = substringBefore( 'beep boop', ' ' );
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* // returns 'beep'
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*
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* @example
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* var out = substringBefore( 'beep boop', 'p' );
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* // returns 'bee'
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*
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* @example
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* var out = substringBefore( 'Hello World!', '' );
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* // returns ''
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*
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* @example
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* var out = substringBefore( 'Hello World!', 'XYZ' );
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* // returns 'Hello World!'
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*/
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function substringBefore( str, search ) {
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var idx;
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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 ( !isString( search ) ) {
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throw new TypeError( format( 'invalid argument. Second argument must be a string. Value: `%s`.', search ) );
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}
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idx = str.indexOf( search );
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if ( idx === -1 ) {
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return str;
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}
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return str.substring( 0, idx );
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}
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// EXPORTS //
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module.exports = substringBefore;
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