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node_modules/when/pipeline.js 1.47 KB
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  /** @license MIT License (c) copyright 2011-2013 original author or authors */
  
  /**
   * pipeline.js
   *
   * Run a set of task functions in sequence, passing the result
   * of the previous as an argument to the next.  Like a shell
   * pipeline, e.g. `cat file.txt | grep 'foo' | sed -e 's/foo/bar/g'
   *
   * @author Brian Cavalier
   * @author John Hann
   */
  
  (function(define) {
  define(function(require) {
  
  	var when = require('./when');
  	var all = when.Promise.all;
  	var slice = Array.prototype.slice;
  
  	/**
  	 * Run array of tasks in a pipeline where the next
  	 * tasks receives the result of the previous.  The first task
  	 * will receive the initialArgs as its argument list.
  	 * @param tasks {Array|Promise} array or promise for array of task functions
  	 * @param [initialArgs...] {*} arguments to be passed to the first task
  	 * @return {Promise} promise for return value of the final task
  	 */
  	return function pipeline(tasks /* initialArgs... */) {
  		// Self-optimizing function to run first task with multiple
  		// args using apply, but subsequence tasks via direct invocation
  		var runTask = function(args, task) {
  			runTask = function(arg, task) {
  				return task(arg);
  			};
  
  			return task.apply(null, args);
  		};
  
  		return all(slice.call(arguments, 1)).then(function(args) {
  			return when.reduce(tasks, function(arg, task) {
  				return runTask(arg, task);
  			}, args);
  		});
  	};
  
  });
  })(typeof define === 'function' && define.amd ? define : function (factory) { module.exports = factory(require); });