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09.1 datatypes in js.html
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09.1 datatypes in js.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Data types in js</title>
</head>
<body>
<!-- https://www.w3schools.com/js/js_datatypes.asp
JavaScript has 8 Datatypes The Object Datatype
1. String The object data type can contain:
2. Number 1. An object
3. Bigint 2. An array
4. Boolean 3. A date
5. Undefined
6. Null
7. Symbol
8. Object
-->
<script>
// Numbers:
let length = 16;
let weight = 7.5;
console.log(length,"and",weight);
// Strings:
let color = "Yellow";
let lastName = "Johnson";
console.log(color);
// Booleans
let x = true;
let y = false;
console.log(x);
// Object:
const person = {firstName:"Muazim", lastName:"Maqbool"};
console.log(person)
// Array:
const cars = ["Saab", "Volvo", "BMW"];
console.log(cars)
// Date object:
const date = new Date(); // will give current date
console.log(date)
const time=date.toLocaleTimeString(); //will give current local time
//or
//const time=new Date().toLocaleTimeString();
console.log(time);
//Note!
let result= 16 + "laptop";
//JavaScript will treat the example above as: let result="16" + "laptop";
//When adding a number and a string, JavaScript will treat the number as a string.
console.log(result) // o/p: 16laptop
//same goes with : let result="laptop" + 16 ; o/p: laptop16
//Note!
//JavaScript evaluates expressions from left to right. Different sequences can produce different
//results:
let output=16+4+ "Desktop";
console.log(output); // o/p: 20Desktop
//JavaScript treats 16 and 4 as numbers, until it reaches "Desktop" , then result of previous truns to string
//Note!
let output1="Desktop"+ 16+4;
console.log(output1); // o/p: Desktop164
//since the first operand is a string, then all operands are treated as strings.
//JavaScript Types are Dynamic
//JavaScript has dynamic types. This means that the same variable can be used to hold different
//data types:
let a; // Now a is undefined
a = 5; // Now a is a Number
a = "printer"; // Now a is a String
console.log(a); // o/p: printer
//JavaScript BigInt
//All JavaScript numbers are stored in a a 64-bit floating-point format.
//JavaScript BigInt is a new datatype (2020) that can be used to store integer values that
//are too big to be represented by a normal JavaScript Number.
let b = BigInt("123456789012345678901234567890");
console.log(b);
//JavaScript Objects - important
//JavaScript objects are written with curly braces {}.
//Object properties are written as name:value pairs, separated by commas.
//Objects are used to store named values
const item={
name:"Hp laptop",
model:"2018",
ram:"8GB",
processor:"i3"
}
console.log(item);
//The object (item) in the example above has 4 properties: name,model,ram,processor
console.log("the product is: "+item.name+" it has "+item.ram); // or use , in place of +
//The typeof Operator
//You can use the JavaScript typeof operator to find the type of a JavaScript variable.
//The typeof operator returns the type of a variable or an expression:
console.log(typeof(""));
console.log(typeof("laptop"));
console.log(typeof "mobile phone");
console.log(typeof 0);
console.log(typeof 12);
console.log(typeof 3.14);
let z=true;
console.log(typeof z);//boolean
</script>
</body>
</html>