Simple, isolated sync/async waterfall module for JavaScript.
Runs an array of functions in series, each passing their results to the next in the array. However, if any of the functions pass an error to the callback, the next function is not executed and the main callback is immediately called with the error.
For browsers and node.js.
npm install a-sync-waterfall if you’re using node.js.waterfall(tasks, optionalCallback, forceAsync);callback(err, result1, result2, ...) it must call on completion. The first
argument is an error (which can be null) and any further arguments will be
passed as arguments in order to the next task.javascript
var waterfall = require('a-sync-waterfall');
waterfall(tasks, callback);
```javascript var waterfall = require('a-sync-waterfall'); waterfall(tasks, callback);
// Default: window.waterfall(tasks, callback); ```
javascript
waterfall([
function(callback){
callback(null, 'one', 'two');
},
function(arg1, arg2, callback){
callback(null, 'three');
},
function(arg1, callback){
// arg1 now equals 'three'
callback(null, 'done');
}
], function (err, result) {
// result now equals 'done'
});
```javascript / basic - no arguments / waterfall(myArray.map(function (arrayItem) { return function (nextCallback) { // same execution for each item, call the next one when done doAsyncThingsWith(arrayItem, nextCallback); }}));
/ with arguments, initializer function, and final callback / waterfall([function initializer (firstMapFunction) { firstMapFunction(null, initialValue); }].concat(myArray.map(function (arrayItem) { return function (lastItemResult, nextCallback) { // same execution for each item in the array var itemResult = doThingsWith(arrayItem, lastItemResult); // results carried along from each to the next nextCallback(null, itemResult); }})), function (err, finalResult) { // final callback }); ```
Hat tip to Caolan McMahon and Paul Miller, whose prior contributions this is based upon. Also Elan Shanker from which this rep is forked