Package Exports

@stdlib/utils-async-try-then
@stdlib/utils-async-try-then/dist
@stdlib/utils-async-try-then/dist/index.js
@stdlib/utils-async-try-then/lib/index.js

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (@stdlib/utils-async-try-then) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

About stdlib...

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trythenAsync

If a function does not return an error, invoke a callback with the function result; otherwise, invoke a second function.

Installation

npm install @stdlib/utils-async-try-then

Usage

var trythenAsync = require( '@stdlib/utils-async-try-then' );

trythenAsync( x, y, done )

If a function x does not return an error, invokes a done callback with the function result; otherwise, invokes a second function y.

var randu = require( '@stdlib/random-base-randu' );

function x( clbk ) {
    setTimeout( onTimeout, 0 );
    function onTimeout() {
        if ( randu() > 0.5 ) {
            return clbk( null, 1.0 );
        }
        clbk( new Error( 'oops' ) );
    }
}

function y( clbk ) {
    setTimeout( onTimeout, 0 );
    function onTimeout() {
        clbk( null, -1.0 );
    }
}

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

trythenAsync( x, y, done );

The function x is provided a single argument:

clbk: callback to invoke upon function completion.

var randu = require( '@stdlib/random-base-randu' );

function x( clbk ) {
    setTimeout( onTimeout, 0 );
    function onTimeout() {
        clbk( null, 1.0, 2.0, 3.0 );
    }
}

function y( clbk ) {
    setTimeout( onTimeout, 0 );
    function onTimeout() {
        clbk( null, 4.0, 5.0, 6.0 );
    }
}

function done( error, a, b, c ) {
    if ( error ) {
        throw error;
    }
    console.log( a, b, c );
}

trythenAsync( x, y, done );

If the error argument is truthy, the function invokes y. The number of arguments provided to y depends on the function's length. If y is a unary function, y is provided a single argument:

clbk: callback to invoke upon function completion.

Otherwise, y is provided two arguments:

error: the error from x.
clbk: callback to invoke upon function completion.

The callback function accepts any number of arguments, with the first argument reserved for providing an error. If the error argument is falsy, the done callback is invoked with its first argument equal to null and all other provided arguments. If the error argument is truthy, the done callback is invoked with only the error argument provided by y.

var randu = require( '@stdlib/random-base-randu' );

function x( clbk ) {
    setTimeout( onTimeout, 0 );
    function onTimeout() {
        if ( randu() > 0.5 ) {
            return clbk( null, 1.0, 2.0, 3.0 );
        }
        clbk( new Error( 'beep' ) );
    }
}

function y( clbk ) {
    setTimeout( onTimeout, 0 );
    function onTimeout() {
        if ( randu() > 0.5 ) {
            return clbk( null, 4.0, 5.0, 6.0 );
        }
        clbk( new Error( 'boop' ) );
    }
}

function done( error, a, b, c ) {
    if ( error ) {
        console.error( error.message );
    }
    console.log( a, b, c );
}

trythenAsync( x, y, done );

Notes

Execution is not guaranteed to be asynchronous. To guarantee asynchrony, 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 randu = require( '@stdlib/random-base-randu' );
var ceil = require( '@stdlib/math-base-special-ceil' );
var repeatString = require( '@stdlib/string-repeat' );
var trythenAsync = require( '@stdlib/utils-async-try-then' );

var i;

function next() {
    trythenAsync( x, y, done );
}

function x( clbk ) {
    setTimeout( onTimeout, 0 );
    function onTimeout() {
        if ( randu() > 0.9 ) {
            return clbk( null, repeatString( 'BOOP', ceil( randu()*3.0 ) ) );
        }
        clbk( new Error( 'oops' ) );
    }
}

function y( clbk ) {
    setTimeout( onTimeout, 0 );
    function onTimeout() {
        clbk( null, repeatString( 'beep', ceil( randu()*5.0 ) ) );
    }
}

function done( error, result ) {
    if ( error ) {
        throw error;
    }
    i += 1;
    console.log( result );
    if ( i < 100 ) {
        return next();
    }
}

i = 0;
next();

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

License

See LICENSE.

@stdlib/utils-async-try-then