Working with data

In javascript we define a variable with var. Once you define a variable, we can initialize it. We do not need to explicitly declare the data type (like whether integer, float or string). The data type is determined when you assign a value. We can check the datatype following way:

> var pi = 3.14; 
  console.log(typeof pi)

number

Common arithmetic operations

var a = 5; 
var b = 7; 
var sum = 5 + 7; 
console.log(sum)

12

var a = 3; 
var b = 9; 
var c = 6; 
var result = a + b*c 
console.log(result)

57

Some shorthand notations

a = a + 4; 
a += 4; 

The above works with +, -, *, /

a = a + 1; 
a++; 

a = a -1; 
a--;

String concatenation

var greeting = "Hello "; 
var name = "Pranab"; 

console.log(greeting + name)

Hello Pranab

Be careful to check the data type while using operators. Notice the following:

var a = "4"; // this a string 
var b = 5; 

var sum = a + b; 
var sub = a - b; 
var mult = a * b; 

console.log("sum = " + sum + ", sub =" + sub + ", mult =" + mult)

sum = 45, sub =-1, mult =20

Notice the string concatenation in case of addition, however subtraction and multiplication carried out properly even though a was a string. Obviously, it works only when the string contains only numbers.