83 lines
2.1 KiB
JavaScript
83 lines
2.1 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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// VARIABLES //
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var SORT_OPTS = {
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'numeric': true // Use numeric collation such that "1" < "2" < "10"...
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};
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// FUNCTIONS //
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/**
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* Comparator function to sort values in ascending order.
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*
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* @private
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* @param {*} a - first value
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* @param {*} b - second value
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* @returns {number} negative number if `a` comes before `b, positive if `a` comes after `b`, and `0` if they are equivalent
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*/
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function ascending( a, b ) {
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return String( a ).localeCompare( String( b ), void 0, SORT_OPTS );
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}
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// MAIN //
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/**
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* Returns the unique elements in an array.
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*
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* @private
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* @param {Array} arr - input array
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* @returns {Array} array of unique elements
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*/
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function unique( arr ) {
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var len;
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var out;
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var val;
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var i;
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var j;
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// Copy the array to avoid mutation:
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out = Array.prototype.slice.call( arr );
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len = out.length;
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// Sort array in ascending order:
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out.sort( ascending );
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// Loop through the array, only incrementing a pointer when successive values are different. When a succeeding value is different, move the pointer and set the next value. In the trivial case where all array elements are unique, we incur a slight penalty in resetting the element value for each unique value. In other cases, we simply move a unique value to a new position in the array. The end result is a sorted array with unique values.
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for ( i = 1, j = 0; i < len; i++ ) {
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val = out[ i ];
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if ( out[ j ] !== val ) {
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j += 1;
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out[ j ] = val;
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}
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}
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// Truncate the array:
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out.length = j+1;
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return out;
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}
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// EXPORTS //
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module.exports = unique;
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