why we use function in js code example

Example 1: how to use function in javascript

/* Declare function */
function myFunc(param) {
  // Statements 
}

Example 2: javascript function

var x = myFunction(10, 10);     // Function is called, return value will end up in x

function myFunction(a, b) {
    return a * b;             // Function returns the product of a and b
}