Learn Typescript Logical operators & Examples
- Admin
- Sep 20, 2023
- Typescript
Typescript Boolean operators
Logical operators
are basic operators in a programming language.
They compare Boolean expressions and return Boolean values. Boolean expressions are multiple conditions where each condition returns true/false. Then these conditions can be combined using this logical operator, the output result is A Boolean.
The syntax and usage are the same in javascript too.
This operator is also called the boolean operator in typescript.
Here is a boolean operator syntax
.
Operand operator operand
The operand is an expression that evaluates to true/false.
Three logical operators in typescript are And
, OR
, and Not
.
Typescript Logical OR Operator
The symbol for this operator is two vertical lines(||
).
The operand is a conditional expression which a boolean.
We can combine multiple operands, precedence is from left to right.
Here are the possible conditional values for OR operator examples
console.log(true || true); // returns true
console.log(false || true); // returns true
console.log(true || false); // returns true
console.log("string1" || "string2"); // returns "string1"
console.log(false || "string3"); // returns "string3"
console.log("string4" || false); // returns "string4"
console.log("" || false); // returns false
console.log(false || ""); // returns ""
if one of the operators is true
, then output returns true
or else returns false
.
All the expressions return true
except for both using the false
condition.
Important notes:
- The operator always calculates from left to right
- If the first operand is true and the remaining operand doe not evaluated, the operator returns true.
- if all operand evaluates it means subsequent operands from the left are false.
Typescript Logical And Operator
And the operator symbol is double ampersands
(&&
).
This operator returns true
if all the operands are evaluated as true
. else return false
.
console.log(true && true); // returns true
console.log(false && true); // returns false
console.log(true && false); // returns false
console.log("string1" && "string2"); // returns "string2"
console.log(false && "string3"); // returns "false"
console.log("string4" && false); // returns "false"
console.log("" && false); // returns ""
console.log(false && ""); // returns false
Important notes:
- Always evaluates from left to right
- if the first operand evaluates as false, returns false and other operations are not evaluated.
- if all expressions evaluate, it returns the last operand evaluated value as output
Typescript Logical Not Operator
Not
the operator symbol is an exclamation mark !
.
This operator returns the inverse of the operand value.
console.log(!true); // returns false
console.log(!false); // returns true
Conclusion
In this tutorial, Learned a Logical operator with examples. And also expressions are evaluated from left to right for these operators.