weachy

A tiny (17 lines of code) async waterfall implementation that supports CommonJS, AMD, and VanillaJS. The minified file weachy.min.js is just 355 bytes.

Install

npm

npm install weachy

bower

bower install weachy

Usage

waterfall(array, callback, context)

Arguments

• array - An array of functions that take a callback(err, result1, result2, ...) as the last argument. The arguments preceeding the callback are the results of the previous function in the array.
• callback(err, result1, result2, ..., resultn) - The callback that is called when all functions in the array are finished or an error occurs.
• context (optional) - The context to be used when calling each function in the array.

Examples

Browser (No module loader)

<script src="/js/weachy.js"></script>
<script>
  // waterfall is a global bound to the window object now
  waterfall([
    function(next) {
      done(null, 1, 2, 3);
    },
    function(num1, num2, num3, next) {
      done(null, num1 + num2, num3);
    }
  ], function(err, sum, num3) {
    console.log(sum);
    // 3
    console.log(num3);
    // 3
  });
</script>

Node.js

var waterfall = require('weachy');
var jsdom = require('jsdom');
var fs = require('fs');

var url = process.argv[2];

waterfall([
  function(next) {
    fs.readFile('./jquery.js', 'utf-8', next);
  },
  function(jquery, next) {
    jsdom.env({
      url: url,
      src: [jquery],
      done: next
    });
  },
  function(window, next) {
    // Get a reference to jQuery
    var $ = window.$;
    var images = $('img').map(function() {
      return this.src;
    });
    // Convert a NodeList to an array
    next(null, Array.prototype.slice.call(images));
  }
], function(err, imageUrls) {
  if (err) {
    console.error(err);
    return process.exit(1);
  }
  var filename = 'images-' + Date.now() + '.txt';
  fs.writeFile(filename, imageUrls.join('\n'), function(err) {
    if (err) console.error(err);
    else console.log(filename);
    // Type coercion to go undefined|Error -> bool -> number
    process.exit(+!!err);    
  });
});