Decision

Decision is a library for making decision trees.

What are decision trees?

Decision trees are simply trees of questions.

How to code using this library?

OK, firstup, we need to create a decision tree, like this:

const tree = decision.createDecisionTree();
let message; // We need to store the output ourselves

Next, we can add a question using the addQuestion() function. addQuestion() takes 4 arguments:

• name (String): the keyword with which we access the question
• condition (Function)
  • tree: the decision tree itself
  • input: what we're feeding into the decision tree
  • Returns true if you want to answer the question as yes, and false otherwise
• callback1 (Function): What the library executes when the answer is yes
  • tree: the decision tree itself
• callback2 (Function) (optional): What the library executes when the answer is no
  • tree: the decision tree itself

We can also use the function goto(), which just takes a single argument:

• name (String): The question we want to go to

Now, we can write our code like this:

const tree = decision.createDecisionTree();
let message;

tree.addQuestion('is it snowing', (tree, info) => info.snowing, tree => {	
	tree.goto('is it hailing');
}, tree => {
	tree.goto('is it sunny');
});

tree.addQuestion('is it hailing', (tree, info) => info.hailing, tree => {
	message = 'yes, it\'s raining';
}, tree => {
	message = 'no, it\'s not raining';
});

tree.addQuestion('is it sunny', (tree, info) => info.sunny, tree => {
	message = 'no, it\'s not raining';
}, tree => {
	tree.goto('is it windy');
});

tree.addQuestion('is it windy', (tree, info) => info.windy, tree => {
	message = 'no, it\'s not raining';
}, tree => {
	message = 'yes, it\'s raining';
});

Great! Now that we have our decision tree, we can actually use it, using the exec() function. exec(), like goto(), just takes a single argument:

• input: What we want to feed into the decision tree

This makes the final code the following:

const tree = decision.createDecisionTree();
let message;

tree.addQuestion('is it snowing', (tree, info) => info.snowing, tree => {	
	tree.goto('is it hailing');
}, tree => {
	tree.goto('is it sunny');
});

tree.addQuestion('is it hailing', (tree, info) => info.hailing, tree => {
	message = 'yes, it\'s raining';
}, tree => {
	message = 'no, it\'s not raining';
});

tree.addQuestion('is it sunny', (tree, info) => info.sunny, tree => {
	message = 'no, it\'s not raining';
}, tree => {
	tree.goto('is it windy');
});

tree.addQuestion('is it windy', (tree, info) => info.windy, tree => {
	message = 'no, it\'s not raining';
}, tree => {
	message = 'yes, it\'s raining';
});

tree.exec({
	snowing: false,
	hailing: false,
	sunny: true,
	windy: false
});

console.log(message);

When we run our code, we should see this in the console:

no, it's not raining

And if we tweak the exec() part a little bit:

tree.exec({
	snowing: true,
	hailing: true,
	sunny: false,
	windy: false
});

And if we run our code again, we should see this:

yes, it's raining