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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 isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive;
var numGraphemeClusters = require( '@stdlib/string/num-grapheme-clusters' );
var nextGraphemeClusterBreak = require( '@stdlib/string/next-grapheme-cluster-break' );
var format = require( '@stdlib/string/format' );
var round = require( '@stdlib/math/base/special/round' );
var floor = require( '@stdlib/math/base/special/floor' );
// MAIN //
/**
* Truncates a string in the middle to a specified length.
*
* @param {string} str - input string
* @param {integer} len - output string length (including sequence)
* @param {string} [seq='...'] - custom replacement sequence
* @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
* @returns {string} truncated string
*
* @example
* var str = 'beep boop';
* var out = truncateMiddle( str, 5 );
* // returns 'b...p'
*
* @example
* var str = 'beep boop';
* var out = truncateMiddle( str, 5, '>>>' );
* // returns 'b>>>p'
*
* @example
* var str = 'beep boop';
* var out = truncateMiddle( str, 10 );
* // returns 'beep boop'
*
* @example
* var str = 'beep boop';
* var out = truncateMiddle( str, 0 );
* // returns ''
*
* @example
* var str = 'beep boop';
* var out = truncateMiddle( str, 2 );
* // returns '..'
*
* @example
* var str = '🐺 Wolf Brothers 🐺';
* var out = truncateMiddle( str, 7 );
* // returns '🐺 ... 🐺'
*/
function truncateMiddle( str, len, seq ) {
var seqLength;
var fromIndex;
var strLength;
var seqStart;
var nVisual;
var seqEnd;
var idx2;
var idx1;
if ( !isString( str ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a string. Value: `%s`.', str ) );
}
if ( !isNonNegativeInteger( len ) ) {
throw new TypeError( format( 'invalid argument. Second argument must be a nonnegative integer. Value: `%s`.', len ) );
}
if ( arguments.length > 2 ) {
if ( !isString( seq ) ) {
throw new TypeError( format( 'invalid argument. Third argument must be a string. Value: `%s`.', seq ) );
}
}
seq = seq || '...';
seqLength = numGraphemeClusters( seq );
strLength = numGraphemeClusters( str );
fromIndex = 0;
if ( len > strLength ) {
return str;
}
if ( len - seqLength < 0 ) {
return seq.slice( 0, len );
}
seqStart = round( ( len - seqLength ) / 2 );
seqEnd = strLength - floor( ( len - seqLength ) / 2 );
nVisual = 0;
while ( nVisual < seqStart ) {
idx1 = nextGraphemeClusterBreak( str, fromIndex );
fromIndex = idx1;
nVisual += 1;
}
idx2 = idx1;
while ( idx2 > 0 ) {
idx2 = nextGraphemeClusterBreak( str, fromIndex );
if ( idx2 >= seqEnd + fromIndex - nVisual ) {
break;
}
fromIndex = idx2;
nVisual += 1;
}
return str.substring( 0, idx1 ) + seq + str.substring( idx2 );
}
// EXPORTS //
module.exports = truncateMiddle;
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