Adding JavaScript Interactivity to Your HTML Forms

Variables

Variables are the containers for storing information or a data. In Javascript , it can be declared in three ways:

1.var   2.let  3.count

1.var keyword – function scope or global scope. var variables can be re-declared and updated

var x=10
{
var y=20
}
console.log(y)

//output: 20

2. let keyword-block scope. let is only available for use within that block.

{
let x=20
console.log(x)
}

//output:20

3.const keyword – block scope. const cannot be updated or re-declared.

function myscript() {
  const a = 30;
  a = 40; // TypeError: Assignment to constant variable
}

myscript();

Operators

Javascript operators are used to perform operations on values and variables in different types of mathematical and logical computations.

Examples:

Assignment Operator  : = assigns values between the variables

Addition Operator  : + adds values between the variables

Multiplication Operator : * multiplies values between the variables

Comparison Operator : > compares values between the variables

Functions

In JavaScript, function is defined with the function keyword, followed by a name, followed by parentheses () designed to perform a particular tasks. The parentheses may include parameter names separated by commas like (a,b…)

Parameters refers to the variables or placeholder that you define when declaring a function. It serves as a inputs to the function and allows to pass data into a function.

function area(l,b)
{
  result=l*b
  console.log(result)
}
area(10,5)

//output:50