async/lib/forever.js at gh-pages · againksy/async

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import noop from 'lodash/noop';

import onlyOnce from './internal/onlyOnce';

import ensureAsync from './ensureAsync';

/**

* Calls the asynchronous function `fn` with a callback parameter that allows it

* to call itself again, in series, indefinitely.

* If an error is passed to the

* callback then `errback` is called with the error, and execution stops,

* otherwise it will never be called.

* @name forever

* @static

* @memberOf module:ControlFlow

* @method

* @category Control Flow

* @param {Function} fn - a function to call repeatedly. Invoked with (next).

* @param {Function} [errback] - when `fn` passes an error to it's callback,

* this function will be called, and execution stops. Invoked with (err).

* @example

* async.forever(

* function(next) {

* // next is suitable for passing to things that need a callback(err [, whatever]);

* // it will result in this function being called again.

* },

* function(err) {

* // if next is called with a value in its first parameter, it will appear

* // in here as 'err', and execution will stop.

* }

* );

export default function forever(fn, errback) {

var done = onlyOnce(errback || noop);

var task = ensureAsync(fn);

function next(err) {

if (err) return done(err);

task(next);

}

next();

}