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Every variable has a data type that determines type of value it stores, a variable of type number can store an integer or floating-point numbers.
JavaScript is dynamically typed language which means a variable can be number type for a moment and at another be a string type.
Number
number
type represents both integer and fractional (floating point numbers).
let num = 79; // integer
let num = 65.45; // floating-point
We can perform arithmetic operations like +
, -
, *
, /
.
let num = 45 + 2 * 6; // 57
For very big number or very small number, we can use e
(exponent)
let speedOfLight = 2.998e8;
Infinity
represents mathematical infinity, this is a special numeric value.
let infinity = 1 / 0;
console.log(infinity); // Infinity
NaN
is also a special numeric value to represent the incorrect or invalid mathematical operation.
let nan = "str" / 79;
We can get the data type of a variable using
typeof
.console.log(typeof "peace"); //string
String
string
is used to represent text. They are written by eclosing them their content in quotes.
let hello = "Hello World";
let sq = 'sinle quote';
Both single quote and double quote can be used.
Backticks represents string template, we can embed variable and expression in a string by enclosing them in ${ variable or expression }
expression inside ${....}
is evaluated and becomes a part of the string.
let name = "Kevin";
console.log(`My name is ${ name } `); // My name is kevin
console.log(`Age is ${17 + 1} `); // Age is 18
Boolean
Boolean type has two values only: true
and false
.
It is used to store yes/ no values.
let isGreater = true;
null
To represent nothingness, empty, we can use null
let answer = null;
undefined
if a value is not assigned to a variable or variable is not declared , it will have undefined
.
Meaning of undefined
is "value is not assigned".
let a;
console.log(a) //undefined
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