Comments in Javascript:
There are two ways to comments on Javascript. Single line comment and multiline comment. To start with a single line comment in one line. here is the sample: //This is single-line comment
Multiline comment means you can comment through two to more lines you want. sample is:
/*This is
multiline
comment
*/
Variable in JavaScript:
we can call the variable in three ways. They are var
, let
, and const
var
and const
use for reassigning a variable Where const
can’t reassignable.
For example :
const name = " John";
var city = "Miami";
let city = " Calfornia"
one more thing to remember the variable name cannot start with numbers. To multi-words variable, there are three ways
- Camel case:
var firstName = " john";
- Underscore:
var frist_name = "john";
- pascal case:
var FirstName = "John";
Data type:
There are two types of data types in Javascript.
- Primitive Datatype :
- The value stored directly in the location variable access.
- stored on the heap.
- Example: strings, numbers, boolean, null, undefine, symbols(ES6).
- Reference Datatype:
- access by reference.
- a pointer to a location in memory
- an object that is stored on the heap.
- Example: arrays, objects, functions, dates, etc.
String: Any text which covered with ""
is a string in javascript. for example: const name = "John"
.
Numbers: All numeric are numbers in Javascript. Example: const age: 34;
Booleans: true
and false
are boolean. sometimes its work as 0
and 1
Array: Array uses to store multiple items in javascript. Example: const fruits = ["apple", "banana", "seed"];
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