We will be covering 3 topics in this chapter

Chapter 1.2 - Data types

1. Primitive Values v/s Objects
2. Undefined and Null
3. Type of Results

Primitive Values Vs Objects

• Primitive types in JavaScript are of 5 types

1. strings
2. numbers (Number and BigInt)
3. booleans (true or false)
4. undefined
5. Symbol values

null is a special primitive type. If you run typeof null you’ll get object back, but it’s actually a primitive type.

• Everything that is not a primitive type is an Object.

• A major difference Between the two is how they are compared, as each object has a unique identity and is only (strictly) equal to itself. we can se a code explaining the same below

var object1 = {}; // empty obj 1
var object2 = {}; // empty obj 2
console.log(object1 === object2); // false
console.log(object1 === object1); // true

Undefined and Null

Most programming languages have values denoting missing information. JavaScript has two such “nonvalues” : undefined and null

• undefined means “no value.”

1. Uninitialized variables are undefined:

var x;
console.log(x); // undefined

2. Missing parameters are undefined

function sum(a, b) {
  console.log(a); // undefined
  console.log(b); // undefined
}
sum(); // point of execution

function sum(a, b) {
  console.log(a); // 5
  console.log(b); // undefined
}
sum(5); // point of execution

function sum(a, b) {
  console.log(a); // 5
  console.log(b); // 6
}
sum(5, 6); // point of execution

3. If you read a nonexistent property, you get undefined

const obj = {};
console.log(obj.firstName); //undefined

• null means “no object” . It is used as a nonvalue whenever a object is expected (parameters ,last i a chain of objects etc.)

function countLength(obj) {
  return Object.keys(obj).length;
}
console.log(countLength({ a: 5 })); // 1

when we dont have a object

function countLength(obj) {
  if (obj === null) {
    throw new Error("Expected an object"); // Uncaught Error: Expected an object"
  }
  return Object.keys(obj).length;
}
console.log(countLength(null));

Type of Results

typeof results