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    @stdlib/iter-for-each
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    0.0.6 • Public • Published

    forEach Iterator

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    Create an iterator which invokes a function for each iterated value before returning the iterated value.

    Installation

    npm install @stdlib/iter-for-each

    Usage

    var iterForEach = require( '@stdlib/iter-for-each' );

    iterForEach( iterator, fcn[, thisArg] )

    Returns an iterator which invokes a function for each iterated value before returning the iterated value.

    var array2iterator = require( '@stdlib/array-to-iterator' );
    
    function assert( v ) {
        if ( v !== v ) {
            throw new Error( 'should not be NaN' );
        }
    }
    
    var it = iterForEach( array2iterator( [ 1, 2, 3, 4 ] ), assert );
    // returns <Object>
    
    var r = it.next().value;
    // returns 1
    
    r = it.next().value;
    // returns 2
    
    r = it.next().value;
    // returns 3
    
    // ...

    The returned iterator protocol-compliant object has the following properties:

    • next: function which returns an iterator protocol-compliant object containing the next iterated value (if one exists) assigned to a value property and a done property having a boolean value indicating whether the iterator is finished.
    • return: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.

    The invoked function is provided two arguments:

    • value: iterated value
    • index: iteration index (zero-based)
    var array2iterator = require( '@stdlib/array-to-iterator' );
    
    function assert( v ) {
        if ( v !== v ) {
            throw new Error( 'should not be NaN' );
        }
    }
    
    var it = iterForEach( array2iterator( [ 1, 2, 3, 4 ] ), assert );
    // returns <Object>
    
    var r = it.next().value;
    // returns 1
    
    r = it.next().value;
    // returns 2
    
    r = it.next().value;
    // returns 3
    
    // ...

    To set the function execution context, provide a thisArg.

    var array2iterator = require( '@stdlib/array-to-iterator' );
    
    function assert( v ) {
        this.count += 1;
        if ( v !== v ) {
            throw new Error( 'should not be NaN' );
        }
    }
    
    var ctx = {
        'count': 0
    };
    
    var it = iterForEach( array2iterator( [ 1, 2, 3, 4 ] ), assert, ctx );
    // returns <Object>
    
    var r = it.next().value;
    // returns 1
    
    r = it.next().value;
    // returns 2
    
    r = it.next().value;
    // returns 3
    
    var count = ctx.count;
    // returns 3

    Notes

    • If an environment supports Symbol.iterator and a provided iterator is iterable, the returned iterator is iterable.

    Examples

    var randu = require( '@stdlib/random-iter-randu' );
    var isnan = require( '@stdlib/math-base-assert-is-nan' );
    var iterForEach = require( '@stdlib/iter-for-each' );
    
    var rand;
    var it;
    var r;
    
    function assert( v ) {
        if ( isnan( v ) ) {
            throw new Error( 'should not be NaN' );
        }
    }
    
    // Create a seeded iterator for generating pseudorandom numbers:
    rand = randu({
        'seed': 1234,
        'iter': 10
    });
    
    // Create an iterator which validates generated numbers:
    it = iterForEach( rand, assert );
    
    // Perform manual iteration...
    while ( true ) {
        r = it.next();
        if ( r.done ) {
            break;
        }
        console.log( r.value );
    }

    Notice

    This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

    For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

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    License

    See LICENSE.

    Copyright

    Copyright © 2016-2021. The Stdlib Authors.

    Install

    npm i @stdlib/iter-for-each

    Homepage

    stdlib.io

    DownloadsWeekly Downloads

    9

    Version

    0.0.6

    License

    Apache-2.0

    Unpacked Size

    44.8 kB

    Total Files

    9

    Last publish

    Collaborators

    • stdlib-bot
    • kgryte
    • planeshifter
    • rreusser