Javascript basics
JavaScript is a programming language that is used to create interactive effects within web browsers.
It is a high-level, interpreted programming language that conforms to the ECMAScript specification.
JavaScript is a loosely typed language that is dynamically typed at runtime. This means that a variable declared as a number can be reassigned to a string.
JavaScript is a multi-paradigm language that supports object-oriented, imperative, and functional programming styles.
Here are some of the most important features of JavaScript:
Variable Declaration
Variables are used to store values. To declare a variable in JavaScript, you use the var
, let
, or const
keyword followed by the variable name and optional initial value.
As an example:
var myVar = "Hello World";
let myLet = 10;
const myConst = true;
Assignment
Assigning a value to a variable is done using the =
operator.
As an example:
myVar = "Goodbye World";
Conditional Statements
Conditional statements are used to execute different blocks of code based on a condition. The if
, else if
, and else
statements are used for this purpose.
As an example:
if (x > 10) {
console.log("x is greater than 10");
} else {
console.log("x is less than or equal to 10");
}
Loops
Loops are used to execute a block of code repeatedly. The for
loop and the while
loop are two common types of loops in JavaScript.
As an example:
for (let i = 0; i < 10; i++) {
console.log(i);
}
let i = 0;
while (i < 10) {
console.log(i);
i++;
}
Functions
Functions are blocks of code that can be reused throughout a program. They can take input arguments and return output values.
As an example:
function add(x, y) {
return x + y;
}
console.log(add(2, 3)); // outputs 5
Comments
Comments are used to add notes to the code that are not executed. They can be single-line or multi-line.
As an example:
// This is a single-line comment
/*
This is a
multi-line comment
*/
JavaScript Programs
A JavaScript program is a collection of JavaScript statements that perform a specific task.
// Prompt the user for their name
let name = prompt("What is your name?");
// Display a greeting message
alert("Hello, " + name + "!");
In this example:
The
prompt()
function is used to display a dialog box to the user asking for their name. The user's response is stored in thename
variable.The
alert()
function is used to display a dialog box with a greeting message that includes the user's name.