for example - encapsulate callback in this context with step

weaselSteps.js

var step = require("step");

var weasel1 = function(callback) {
	callback(null, 'first');
}

var weasel2 = function(callback) {
	callback(null, 'second');
}

var combineWeasel = function(a,b, callback) {
	callback(null, a + ', ' + b + ' weasel.');
}

step(function(){
		weasel1(this.parallel());
		weasel2(this.parallel());
	},
	function(err, a, b) {
		combineWeasel(a, b, this);
	},
	function(err, c) {
		console.log(c);
	}
)