Traditional Function Lab

A function that receives one arg. It returns a value.
It simply doubles the arg, and returns the result.

function doubleIt(x) {
	return 2 * x;
}

//call function
const a = doubleIt(100);
//200

Multiple Args

A function that receives multiple args. It returns a value.
It simply adds the two args, and returns the result.

function computeSum(a, b) {
	return a + b;
}

//call function
const sum = computeSum(10, 5);
//15

Indefinite Number of Args

It is sometimes useful to handle an indefinite number of args (effectively a list). We use what js calls the rest parameter syntax.

function computeSum(...numbers) {
	let sum = 0;
	for (let n of numbers) {
		sum += n;
	}
	return sum;
}

//call function
const sum = computeSum(1, 2, 3);
//6

No Args

We can write a function that receives no args, and returns a value.

function getDefaultWidth() {
	return 10;
}

//call function
const w = getDefaultWidth();
//10

No Return -- With Args

We can write a function that receives args, and returns no value.

function printValue(value) {
	console.log(value);
}

//call function
printValue('Hello');
//output: Hello

No Return -- No Args

We can write a function that receives no args, and returns no value.

function printDefaultWidth() {
	console.log("200");
}

//call function
printDefaultWidth();
//output: 200

Function Expression

In the previous examples we've been declaring functions.

We also have the option of making a function via an expression.

This example shows how.

They can be used interchangeably, but we'll try to use expressions when we only need a function temporarily. If the function could be called from multiple places, we want to declare it.

asExpression() {
	const fct = function(a, b) {
		return a + b;
	};
	
	//run it (on the var)
	const sum = fct(10, 5);
	prn(sum);
	//15
}

Function Expression

In the previous examples we've been declaring functions.

We also have the option of making a function via an expression.

This example shows how.

They can be used interchangeably, but we'll try to use expressions when we only need a function temporarily. If the function could be called from multiple places, we want to declare it.

asExpression() {
	const fct = function(a, b) {
		return a + b;
	};
	
	//run it (on the var)
	const sum = fct(10, 5);
	prn(sum);
	//15
}