Introduction to Functions

Functions take inputs, perform computations, and then return an output. Here is an example of a function that takes two numbers as inputs, adds the numbers, and then returns the sum:

function add(x, y) {
  return(x + y);
}

After a function is defined, it can be invoked to execute the code and get a return value.

console.log(add(3, 4)); // 7

Below is an example of a function that takes a firstName and lastName as inputs, concatenates the strings into a single string, and returns the full name as output:

function fullName(firstName, lastName) {
  return(firstName + ' ' + lastName);
}

Here is how the function can be invoked with the "Matt" and "Powers" arguments:

fullName("Matt", "Powers"); // "Matt Powers"

The following example has comments to explain all the new function jargon.

function silly(x) {
  return(x + 'is silly!');
} // function named silly is defined
silly("dave"); // the silly function is invoked with the argument "dave"

To summarize:

- functions can take zero, one, or more input values
- functions perform computations
- functions return a single value

function subtract(x, y) {
  return(x - y);
}
var r = subtract(100, 4);
console.log(r);

function inchesToCentimeters(n) {
  return(n * 2.54);
}
var r = inchesToCentimeters(10);
console.log(r);

function stringLength(s) {
  return(s.length);
}
var r = stringLength("cool");
console.log(r);