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Waterfall

Execute functions in series, passing the results of one function as arguments to the next function.

Installation

npm install @stdlib/utils-async-series-waterfall

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var waterfall = require( '@stdlib/utils-async-series-waterfall' );

waterfall( fcns, clbk[, thisArg] )

Executes functions in series, passing the results of one function as arguments to the next function.

function foo( next ) {
    next( null, 'beep' );
}

function bar( str, next ) {
    console.log( str );
    // => 'beep'

    next();
}

function done( error ) {
    if ( error ) {
        throw error;
    }
}

var fcns = [ foo, bar ];

waterfall( fcns, done );

To set the this context for all functions in the provided function array, provide a thisArg.

function foo( next ) {
    this.idx = 0;
    next( null, 'beep' );
}

function bar( str, next ) {
    this.idx += 1;
    console.log( str );
    // => 'beep'

    next();
}

function done( error ) {
    if ( error ) {
        throw error;
    }
    console.log( ctx.idx );
    // => 1
}

var ctx = {};
var fcns = [ foo, bar ];

waterfall( fcns, done, ctx );

waterfall.factory( fcns, done[, thisArg] )

Returns a reusable waterfall function.

function foo( next ) {
    next( null, 'beep' );
}

function bar( str, next ) {
    console.log( str );
    // => 'beep'

    next();
}

function done( error ) {
    if ( error ) {
        throw error;
    }
}

var fcns = [ foo, bar ];

var run = waterfall.factory( fcns, done );

run();
run();
run();

Notes

• The last argument applied to each waterfall function is a callback. The callback should be invoked upon a series function completion. The first argument is reserved as an error argument (which can be null). Any results which should be passed to the next function in the series should be provided beginning with the second argument.
• If any function calls the provided callback with a truthy error argument, the waterfall suspends execution and immediately calls the done callback for subsequent error handling.
• This implementation does not guarantee that execution is asynchronous. To do so, wrap the done callback in a function which either executes at the end of the current stack (e.g., nextTick) or during a subsequent turn of the event loop (e.g., setImmediate, setTimeout).

Examples

var replace = require( '@stdlib/string-replace' );
var waterfall = require( '@stdlib/utils-async-series-waterfall' );

function foo( next ) {
    next( null, 'beep' );
}

function bar( str, next ) {
    console.log( str );
    next( null, replace( str, 'e', 'o' ) );
}

function fun( str, next ) {
    console.log( str );
    next();
}

function done( error ) {
    if ( error ) {
        throw error;
    }
    console.log( 'done' );
}

var fcns = [ foo, bar, fun ];

waterfall( fcns, done );

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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.