Functions - arguments and parameters

• Parameters are like placeholders for data that will be passed to a function.

• Arguments are the actual values passed to a function while calling it

function calculateBill(billAmount, taxRate) { // here billAmount, taxRate are parameters
  const total = billAmount + billAmount * taxRate 
  return total;
}

calculateBill(100, 0.13); // here 100, 0.13 are arguments

• Parameters are variables local to the function; available only inside the function.

• You can also pass variables as arguments during a function call.

• We can also pass expressions as arguments to a function.

myTotal3 = calculateBill(20+20+30, 0.3);

• So, we can either pass direct value or variables holding value or expressions resulting in a value to a function as arguments.

• Passing functions as arguments:

function doctorize (name) { 
	return `Dr. ${name}`;
}

function yell (name) {
	return `HEY ${name.toUpperCase()}`;
}

// We can pass a function inside another
yell(doctorize('Soumya')); // HEY DR. SOUMYA
// Above, returned value of doctorize function is passed to yell function

• Default values:

function yell (name = 'Silly Goose') {
	return `HEY ${name.toUpperCase()}`;
}

yell('Soumya') // HEY SOUMYA
yell() // HEY SILLY GOOSE

// Above, if we don't pass any argument to yell function, then it takes the default value in function definition,
// here Silly Goose, else it takes whatever we pass as argument.

• Important gotcha:

function calculateBill(billAmount, taxRate = 0.13, tipRate = 0.15) {
  console.log('Running Calculate Bill!!');
  const total = billAmount + billAmount * taxRate + billAmount * tipRate;
  return total;
}

// Suppose above, we want to pass the tipRate but not the taxRate and want taxRate to be default,
// then the only thing we can do is:
 
calculateBill(100, undefined, 0.66); // here the taxRate will default to 0.13 as 
// we have passed undefined to it and the tipRate will be 0.66 as passed