HTML5 game - decision tree

Most game entity, that you create for your HTML5 games needs our own intelligence. It has to decide what to do next. For example: walks, attacks, speaks, … In this post I show you how to make decision with decision tree.

Consider the following scenario:

	makeDecision() {
	if (iq > 80) {
	negotiation();
	if(comunication > 80){
	win();
	}else{
	loss();
	}
	}else{
	attack();
	if(strength > 80){
	win();
	}else{
	loss();
	}
	}
	}

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This type of the presentation is easy to represent in the form of a tree:

It is better to convert each condition on a separate object. Then you can check the condition and return either a decision or another decision object.

	/**
	* Make a decision
	* @param {string} name
	* @param {number} threshold
	* @param {Object} leNode - less then threshold Node
	* @param {Object} gNode - qrow then threshold Node
	function Decision(name, threshold, leNode, gNode) {
	this._name = name;
	this._threshold = threshold;
	this._leNode = leNode;
	this._gNode = gNode;
	}
	Decision.prototype.execute = function(agent) {
	var node = agent[this._name] > this._threshold ? this._gNode : this._leNode;
	node.execute(agent);
	};

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Finally, you need to create the tree and let it make the decision:

	function Hero(){
	this.inteligence = 100;
	this.communication = 120;
	this.strength = 50;
	}
	function WinAction(){}
	WinAction.prototype.execute = function( hero ){
	console.log("Won");
	}
	function LossAction(){}
	LossAction.prototype.execute = function( hero ){
	console.log("Loss");
	}
	function decisionTree() {
	var winAction = WinAction();
	var lossAction = LossAction();
	return new Decision("inteligence", 80,
	new Decision("strength", 50, lossAction, winAction),
	new Decision("communication", 50, lossAction, winAction));
	}
	var hero = new Hero();
	var tree = decisionTree();
	tree.execute( hero );

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Reference:

• JavaScript Command pattern