A function can have no parameter, like we’ve seen previously:

function test() {
  //do something
}

Or it can have one or more parameters, which are declared inside the parentheses:

function test(color) {
  //do something
}

function test(color, age) {
  //do something
}

When we can pass a parameter, we invoke the function passing arguments:

function test(color, age) {
  //do something
}

test("green", 24)
test("black")

The difference between arguments and parameters is this: you define the parameters and that’s what you see inside the function. Arguments are passed by the program when you call the function.

They are basically the value assigned to the parameter.

Functions can have default values for the parameters that are not passed by the caller:

function test(color = 'red', age = 20) {
  console.log(color, age)
}

test("green", 24)
test("black")

Lessons in this unit: