Skip to content

Latest commit

 

History

History
368 lines (236 loc) · 10.8 KB

README.md

File metadata and controls

368 lines (236 loc) · 10.8 KB
Raw
About stdlib...

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

inmap

NPM version Build Status Coverage Status

Invoke a function for each element in a collection and update the collection in-place.

Usage

To use in Observable,

inmap = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-inmap@umd/browser.js' )

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

var inmap = require( 'path/to/vendor/umd/utils-inmap/index.js' )

To include the bundle in a webpage,

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

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

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

inmap( collection, fcn[, thisArg ] )

Invokes a function for each element in a collection and updates the collection in-place.

function scale( value, index ) {
    return value * index;
}

var arr = [ 1, 2, 3, 4 ];

var out = inmap( arr, scale );
// returns [ 0, 2, 6, 12 ]

var bool = ( out === arr );
// returns true

The invoked function is provided three arguments:

  • value: collection element.
  • index: collection index.
  • collection: input collection.

Basic support for dynamic collections is provided. Note, however, that index incrementation is monotonically increasing.

function scale1( value, index, collection ) {
    if ( index === collection.length-1 && collection.length < 10 ) {
        collection.push( index+2 );
    }
    return value * index;
}

var arr = [ 1, 2, 3, 4 ];

var out = inmap( arr, scale1 );
// returns [ 0, 2, 6, 12, 20, 30, 42, 56, 72, 90 ]

function scale2( value, index, collection ) {
    collection.shift();
    return value * index;
}

arr = [ 1, 2, 3, 4 ];

out = inmap( arr, scale2 );
// returns [ 3, 3 ]

To set the function execution context, provide a thisArg.

function sum( value ) {
    this.sum += value;
    this.count += 1;
    return value;
}

var arr = [ 1, 2, 3, 4 ];

var context = {
    'sum': 0,
    'count': 0
};

var out = inmap( arr, sum, context );
// returns [ 1, 2, 3, 4 ]

var mean = context.sum / context.count;
// returns 2.5

Notes

  • A collection may be either an Array, Typed Array, or an array-like Object (excluding strings and functions).

  • The function differs from Array.prototype.map in the following ways:

    • The function returns the input collection.

    • The function modifies collection elements in-place.

    • The function does not skip undefined elements.

      function log( value, index ) {
    console.log( '%s: %s', index, value );
    return value;
}

var arr = [ 1, , , 4 ];

var out = inmap( arr, log );
/* =>
    0: 1
    1: undefined
    2: undefined
    3: 4
*/

    • The function provides limited support for dynamic collections (i.e., collections whose length changes during execution).

Examples

<!DOCTYPE html>
<html lang="en">
<body>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/assert-is-even@umd/browser.js"></script>
<script type="text/javascript">
(function () {.isPrimitive;
var inmap = require( '@stdlib/utils-inmap' );

var bool;
var arr;
var out;
var i;

function scale( value, index, collection ) {
    if ( isEven( index ) ) {
        collection.shift();
    } else {
        collection.push( index+1 );
    }
    return value * index;
}

arr = new Array( 100 );
for ( i = 0; i < arr.length; i++ ) {
    arr[ i ] = i;
}
out = inmap( arr, scale );

bool = ( out === arr );
console.log( bool );

console.log( out );

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

See Also

  • @stdlib/utils-for-each: invoke a function for each element in a collection.
  • @stdlib/utils-inmap-right: invoke a function for each element in a collection and update the collection in-place, iterating from right to left.
  • @stdlib/utils-map: apply a function to each element in an array and assign the result to an element in an output array.

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

Chat

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.