TypeScript - Operators

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What is an Operator?

An operator defines some function that will be performed on the data. The data on which operators work are called operands. Consider the following expression −

7 + 5 = 12

Here, the values 7, 5, and 12 are operands, while + and = are operators.

The major operators in TypeScript can be classified as −

• Arithmetic operators
• Logical operators
• Relational operators
• Bitwise operators
• Assignment operators
• Ternary/conditional operator
• String operator
• Type Operator

Arithmetic Operators

Assume the values in variables a and b are 10 and 5 respectively.

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Relational Operators

Relational Operators test or define the kind of relationship between two entities. Relational operators return a Boolean value, i.e., true/ false.

Assume the value of A is 10 and B is 20.

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Logical Operators

Logical Operators are used to combine two or more conditions. Logical operators too return a Boolean value. Assume the value of variable A is 10 and B is 20.

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Bitwise Operators

Assume variable A = 2 and B = 3

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Assignment Operators

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Note − Same logic applies to Bitwise operators, so they will become <<=, >>=, >>=, &=, |= and ^=.

Miscellaneous Operators

The negation operator (-)

Changes the sign of a value. Let’s take an example.

var x:number = 4 
var y = -x; 
console.log("value of x: ",x);   //outputs 4 
console.log("value of y: ",y);   //outputs -4

On compiling, it will generate following JavaScript code.

//Generated by typescript 1.8.10
var x = 4;
var y = -x;
console.log("value of x: ", x);   //outputs 4
console.log("value of y: ", y);   //outputs -4

It will produce the following output −

value of x:  4 
value of y:  -4

String Operators: Concatenation operator (+)

The + operator when applied to strings appends the second string to the first. The following example helps us to understand this concept.

var msg:string = "hello"+"world" 
console.log(msg)

On compiling, it will generate following JavaScript code.

//Generated by typescript 1.8.10
var msg = "hello" + "world";
console.log(msg);

It will produce the following output −

helloworld

The concatenation operation doesn’t add a space between strings. Multiple strings can be concatenated in a single statement.

Conditional Operator (?)

This operator is used to represent a conditional expression. The conditional operator is also sometimes referred to as the ternary operator. The syntax is as given below −

Test ? expr1 : expr2

• Test − refers to the conditional expression

• expr1 − value returned if the condition is true

• expr2 − value returned if the condition is false

Let’s take a look at the following code −

var num:number = -2 
var result = num > 0 ?"positive":"non-positive" 
console.log(result)

Line 2 checks whether the value in the variable num is greater than zero. If num is set to a value greater than zero, it returns the string “positive” else the string “non-positive” is returned.

On compiling, it will generate following JavaScript code.

//Generated by typescript 1.8.10
var num = -2;
var result = num > 0 ? "positive" : "non-positive";
console.log(result);

The above code snippet will produce the following output −

non-positive

Type Operators

typeof operator

It is a unary operator. This operator returns the data type of the operand. Take a look at the following example −

var num = 12 
console.log(typeof num);   //output: number

On compiling, it will generate following JavaScript code.

//Generated by typescript 1.8.10
var num = 12;
console.log(typeof num);   //output: number

It will produce the following output −

number

instanceof

This operator can be used to test if an object is of a specified type or not. The use of instanceof operator is discussed in the chapter classes.