77 lines
2.1 KiB
JavaScript
77 lines
2.1 KiB
JavaScript
|
/**
|
||
|
|
* @license Apache-2.0
|
||
|
|
*
|
||
|
|
* Copyright (c) 2018 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 isCollection = require( '@stdlib/assert/is-collection' );
|
||
|
|
var isFunction = require( '@stdlib/assert/is-function' );
|
||
|
|
|
||
|
|
|
||
|
|
// MAIN //
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Applies a function against an accumulator and each element in a collection and returns the accumulated result.
|
||
|
|
*
|
||
|
|
* @param {Collection} collection - input collection
|
||
|
|
* @param {*} initial - initial value
|
||
|
|
* @param {Function} reducer - reduction function
|
||
|
|
* @param {*} [thisArg] - reduction function execution context
|
||
|
|
* @throws {TypeError} first argument must be a collection
|
||
|
|
* @throws {TypeError} third argument must be a function
|
||
|
|
* @returns {*} accumulated result
|
||
|
|
*
|
||
|
|
* @example
|
||
|
|
* function sum( acc, value ) {
|
||
|
|
* return acc + value;
|
||
|
|
* }
|
||
|
|
*
|
||
|
|
* var arr = [ 1, 2, 3, 4 ];
|
||
|
|
*
|
||
|
|
* var s = reduce( arr, 0, sum );
|
||
|
|
* // returns 10
|
||
|
|
*/
|
||
|
|
function reduce( collection, initial, reducer, thisArg ) {
|
||
|
|
var len;
|
||
|
|
var acc;
|
||
|
|
var i;
|
||
|
|
if ( !isCollection( collection ) ) {
|
||
|
|
throw new TypeError( 'invalid argument. First argument must be a collection. Value: `'+collection+'`.' );
|
||
|
|
}
|
||
|
|
if ( !isFunction( reducer ) ) {
|
||
|
|
throw new TypeError( 'invalid argument. Third argument must be a function. Value:`'+reducer+'`.' );
|
||
|
|
}
|
||
|
|
len = collection.length;
|
||
|
|
acc = initial;
|
||
|
|
for ( i = 0; i < len; i++ ) {
|
||
|
|
acc = reducer.call( thisArg, acc, collection[ i ], i, collection );
|
||
|
|
|
||
|
|
// Account for dynamically resizing a collection...
|
||
|
|
if ( len !== collection.length ) {
|
||
|
|
len = collection.length;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return acc;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
// EXPORTS //
|
||
|
|
|
||
|
|
module.exports = reduce;
|