111 lines
3.0 KiB
JavaScript
111 lines
3.0 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 isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive;
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var numGraphemeClusters = require( './../../num-grapheme-clusters' );
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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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* Truncates a string to a specified length.
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*
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* @param {string} str - input string
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* @param {integer} len - output string length (including ending)
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* @param {string} [ending='...'] - custom ending
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* @throws {TypeError} first argument must be a string
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* @throws {TypeError} second argument must be a nonnegative integer
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* @throws {TypeError} third argument must be a string
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* @returns {string} truncated string
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*
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* @example
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* var str = 'beep boop';
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* var out = truncate( str, 7 );
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* // returns 'beep...'
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*
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* @example
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* var str = 'beep boop';
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* var out = truncate( str, 5, '>>>' );
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* // returns 'be>>>'
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*
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* @example
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* var str = 'beep boop';
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* var out = truncate( str, 10 );
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* // returns 'beep boop'
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*
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* @example
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* var str = 'beep boop';
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* var out = truncate( str, 0 );
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* // returns ''
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*
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* @example
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* var str = 'beep boop';
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* var out = truncate( str, 2 );
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* // returns '..'
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*
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* @example
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* var str = '🐺 Wolf Brothers 🐺';
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* var out = truncate( str, 6 );
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* // returns '🐺 W...'
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*/
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function truncate( str, len, ending ) {
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var endingLength;
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var fromIndex;
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var nVisual;
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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 ( !isNonNegativeInteger( len ) ) {
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throw new TypeError( format( 'invalid argument. Second argument must be a nonnegative integer. Value: `%s`.', len ) );
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}
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if ( arguments.length > 2 ) {
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if ( !isString( ending ) ) {
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throw new TypeError( format( 'invalid argument. Third argument must be a string. Value: `%s`.', ending ) );
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}
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}
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ending = ending || '...';
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endingLength = numGraphemeClusters( ending );
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fromIndex = 0;
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if ( len > numGraphemeClusters( str ) ) {
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return str;
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}
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if ( len - endingLength < 0 ) {
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return ending.slice( 0, len );
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}
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nVisual = 0;
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while ( nVisual < len - endingLength ) {
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idx = nextGraphemeClusterBreak( str, fromIndex );
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fromIndex = idx;
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nVisual += 1;
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}
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return str.substring( 0, idx ) + ending;
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}
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// EXPORTS //
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module.exports = truncate;
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