time-to-botec/squiggle/node_modules/@stdlib/utils/async/series-waterfall/README.md

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# Waterfall

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

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<section class="usage">

## Usage

```javascript
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`.

```javascript
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`.

<!-- eslint-disable no-use-before-define -->

```javascript
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`.

```javascript
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();
```

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## 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`).

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## Examples

<!-- eslint no-undef: "error" -->

```javascript
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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