README.md

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iterUntilEach

Create an iterator which, while a test condition is false, invokes a function for each iterated value before returning the iterated value.

Usage

To use in Observable,

iterUntilEach = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/iter-until-each@umd/browser.js' )

The previous example will load the latest bundled code from the umd branch. Alternatively, you may load a specific version by loading the file from one of the tagged bundles. For example,

iterUntilEach = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/iter-until-each@v0.1.0-umd/browser.js' )

To vendor stdlib functionality and avoid installing dependency trees for Node.js, you can use the UMD server build:

var iterUntilEach = require( 'path/to/vendor/umd/iter-until-each/index.js' )

To include the bundle in a webpage,

<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/iter-until-each@umd/browser.js"></script>

If no recognized module system is present, access bundle contents via the global scope:

<script type="text/javascript">
(function () {
    window.iterUntilEach;
})();
</script>

iterUntilEach( iterator, predicate, fcn[, thisArg] )

Returns an iterator which invokes a function for each iterated value before returning the iterated value until either a predicate function returns true or the iterator has iterated over all values.

var array2iterator = require( '@stdlib/array-to-iterator' );

function predicate( v ) {
    return v > 2;
}

function assert( v ) {
    if ( v !== v ) {
        throw new Error( 'should not be NaN' );
    }
}

var it = iterUntilEach( array2iterator( [ 1, 2, 3, 4 ] ), predicate, assert );
// returns {}

var r = it.next().value;
// returns 1

r = it.next().value;
// returns 2

r = it.next().value;
// undefined

// ...

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.

Both the predicate function and the function to invoke for each iterated value are provided two arguments:

• value: iterated value
• index: iteration index (zero-based)

var array2iterator = require( '@stdlib/array-to-iterator' );

function predicate( v ) {
    return v > 2;
}

function assert( v, i ) {
    if ( i > 1 ) {
        throw new Error( 'unexpected error' );
    }
}

var it = iterUntilEach( array2iterator( [ 1, 2, 3, 4 ] ), predicate, assert );
// returns <Object>

var r = it.next().value;
// returns 1

r = it.next().value;
// returns 2

r = it.next().value;
// undefined

// ...

To set the execution context for fcn, 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' );
    }
}

function predicate( v ) {
    return v > 2;
}

var ctx = {
    'count': 0
};

var it = iterUntilEach( array2iterator( [ 1, 2, 3 ] ), predicate, assert, ctx );
// returns <Object>

var r = it.next().value;
// returns 1

r = it.next().value;
// returns 2

var count = ctx.count;
// returns 2

Notes

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

Examples

<!DOCTYPE html>
<html lang="en">
<body>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/random-iter-randu@umd/browser.js"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/math-base-assert-is-nan@umd/browser.js"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/iter-until-each@umd/browser.js"></script>
<script type="text/javascript">
(function () {

function assert( v ) {
    if ( isnan( v ) ) {
        throw new Error( 'should not be NaN' );
    }
}

function predicate( v ) {
    return v <= 0.75;
}

// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
    'seed': 1234,
    'iter': 10
});

// Create an iterator which validates generated numbers:
var it = iterUntilEach( rand, predicate, assert );

// Perform manual iteration...
var r;
while ( true ) {
    r = it.next();
    if ( r.done ) {
        break;
    }
    console.log( r.value );
}

})();
</script>
</body>
</html>

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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.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.