164 lines
3.5 KiB
JavaScript
164 lines
3.5 KiB
JavaScript
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/**
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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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// MODULES //
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var setReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
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var isFunction = require( '@stdlib/assert/is-function' );
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var isCollection = require( '@stdlib/assert/is-collection' );
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var iteratorSymbol = require( '@stdlib/symbol/iterator' );
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// MAIN //
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/**
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* Returns an iterator which iterates over each element in an array-like object.
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*
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* @param {Collection} src - input value
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* @param {Function} [mapFcn] - function to invoke for each iterated value
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* @param {*} [thisArg] - execution context
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* @throws {TypeError} first argument must be an array-like object
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* @throws {TypeError} second argument must be a function
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* @returns {Iterator} iterator
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*
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* @example
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* var iter = array2iterator( [ 1, 2, 3, 4 ] );
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*
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* var v = iter.next().value;
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* // returns 1
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*
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* v = iter.next().value;
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* // returns 2
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*
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* v = iter.next().value;
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* // returns 3
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*
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* // ...
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*/
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function array2iterator( src ) {
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var thisArg;
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var iter;
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var FLG;
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var fcn;
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var i;
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if ( !isCollection( src ) ) {
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throw new TypeError( 'invalid argument. First argument must be an array-like object. Value: `' + src + '`.' );
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}
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if ( arguments.length > 1 ) {
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fcn = arguments[ 1 ];
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if ( !isFunction( fcn ) ) {
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throw new TypeError( 'invalid argument. Second argument must be a function. Value: `' + fcn + '`.' );
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}
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thisArg = arguments[ 2 ];
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}
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i = -1;
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// Create an iterator protocol-compliant object:
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iter = {};
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if ( fcn ) {
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setReadOnly( iter, 'next', next1 );
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} else {
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setReadOnly( iter, 'next', next2 );
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}
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setReadOnly( iter, 'return', end );
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// If an environment supports `Symbol.iterator`, make the iterator iterable:
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if ( iteratorSymbol ) {
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setReadOnly( iter, iteratorSymbol, factory );
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}
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return iter;
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/**
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* Returns an iterator protocol-compliant object containing the next iterated value.
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*
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* @private
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* @returns {Object} iterator protocol-compliant object
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*/
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function next1() {
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i += 1;
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if ( FLG || i >= src.length ) {
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return {
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'done': true
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};
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}
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return {
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'value': fcn.call( thisArg, src[ i ], i, src ),
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'done': false
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};
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}
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/**
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* Returns an iterator protocol-compliant object containing the next iterated value.
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*
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* @private
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* @returns {Object} iterator protocol-compliant object
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*/
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function next2() {
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i += 1;
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if ( FLG || i >= src.length ) {
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return {
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'done': true
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};
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}
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return {
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'value': src[ i ],
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'done': false
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};
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}
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/**
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* Finishes an iterator.
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*
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* @private
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* @param {*} [value] - value to return
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* @returns {Object} iterator protocol-compliant object
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*/
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function end( value ) {
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FLG = true;
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if ( arguments.length ) {
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return {
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'value': value,
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'done': true
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};
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}
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return {
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'done': true
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};
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}
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/**
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* Returns a new iterator.
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*
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* @private
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* @returns {Iterator} iterator
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*/
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function factory() {
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if ( fcn ) {
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return array2iterator( src, fcn, thisArg );
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}
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return array2iterator( src );
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}
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}
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// EXPORTS //
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module.exports = array2iterator;
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