O Level Exam

Operators in Java Script

An expression is a combination of operators operands that can be evaluated. It may also include function calls which return values.

Examples

x = 7.5 // a numeric literal
“Hello India!” // a string literal
false // a Boolean literal
{feet:10, inches:5} // an object literal
[2,5,6,3,5,7] // an array literal
v= m + n; // the variable v
tot // the variable tot

ARITHMETIC OPERATORS

These are used to perform arithmetic/mathematical operations like subtraction, division, multiplication etc. Arithmetic operators work on one or more numerical values (either literals or variables) and return a single numerical value. The basic arithmetic operators are:

 Operator Operator + (Addition) - (Subtraction) * (Multiplication) / (Division) % (Modulus)

Examples

var s = 10 + 20; // result: s=30
var h = 50 * 4; // result: h = 200
var d = 100 / 4; // result: d = 25
var r = 72 % 14; // result: r=2

Increment and decrement operators

These operators are used for increasing or decreasing the value of a variable by 1. Calculations performed using these operators are very fast.

++ Increment (By One)

-- Decrement (By One)

Example

var a = 15;
a++; // result: a = 16
var b = 20;
b—; // result: b = 19

ASSIGNMENT OPERATORS

It assigns the value of its right operand to its left operand. This operator is represented by equal sign(=).

Example

x = 100; // This statement assigns the value 100 to x.

JavaScript also supports shorthand operator for standard operations.

The shorthand operator with example :

 Shorthand operator Example is equivalent to += a + = b a = a + b -= a - = b a = a - b *= a * = b a = a * b /= a / = b a = a / b %= a % = b a = a % b

RELATIONAL (COMPARISON) OPERATORS

Relational Operators are some symbols which return a Boolean value true or false after evaluating the condition. For example x > y; returns a value true is value of variable x is greater than variable y.

Basic JavaScript comparison operators are given in the table below :

 Operator Description Example = = is equal to 4 = = 8 returns false ! = is not equal to 4 ! = 8 returns true > is greater than 8 > 4 returns true < is less than 8 > 4 returns false < = is less than or equal to 8 < = 4 returns false > = is greater than or equal to 8 > = 4 returns true

Relational operators are functional for strings as well. The comparison takes place in alphabetical order. This alphabetical order is based on ASCII number. For example :

 Statement Output “zero” < “one” false “Zero” < “one” true 10 < 5 false, numeric comparison. “10” < “5” true, string comparison. “10” < 5 false, numeric comparison; “Ten” < 5 Error occurs, “Ten” can not be converted into a number

LOGICAL OPERATORS

Logical operators are used for combining two or more conditions. JavaScript has following three logical operators :

 Operator Description with Example && (AND) returns true if both operands are true else it return false. | | (OR) returns false if both operands are false else it returns true. ! (NOT) returns true if the operand is false and false if operand is true.

CONCATENATION OPERATOR

The + operator concatenates two string operands. The + operator gives priority to string operands over numeric operands It works from left to right. The results depend on the order in which operations are performed.

For example :

 Statement Output “Good” + “Morning” “GoodMorning” “5” + “10” “510” “Lucky” + 7 “Lucky7” 4 + 7 + “Delhi” “11Delhi” “Mumbai” + 0 +0+ 7 “Mumbai007”

Conditional Operator ( ? : )

The conditional operator is a special JavaScript operator that takes three operands. Hence, it is also called ternary operator. A conditional operator assigns a value to a variable based on the condition.

Syntax

var_name = (condition) ? v_1 : v_2

If (condition) is true, the value v_1 is assigned to the variable, otherwise, it assigns the value v_2 to the variable.

For example

status = (age >= 18) ? “adult” : “minor”

This statement assigns the value “adult” to the variable status if age is eighteen or more. Otherwise, it assigns the value “minor” to status.

New Operator:

new operator is used to create an instance and allocate memory to a user-defined or predefined object types.

Syntax

ObjectName = new objectType ( param1 [,param2] ...[,paramN])

Example

d = new Date(); // date assigns to object d
r = new rectangle(4, 5, 7, 8);

Delete Operator

The delete operator de-allocates (releases) the memory space that was allocated using the new operator by deleting an object, an object’s property or an element from an array.

The syntax is

delete object_name
delete object_name.property
delete array_name[index]

delete operator can be used to delete variables declared implicitly but not those declared with the var statement. The delete operator returns true if the operation is possible; it returns false if the operation is not possible.

Question : What is difference between java and javascript

Answer : Some people think that Java and JavaScript are same but both are two completely different languages. Java is a general-purpose objectoriented programming language from Sun Microsystems where as JavaScript is an object-based scripting language. Script refers to short programming statements to perform a task.