In programming, it is very common to get scenarios where we need to fulfil multiple conditions to establish a decision.

In this article, I am going to describe, how to use multiple conditions in javascript if statement. 

Prerequisite:

You should have basic programming knowledge in javascript to understand this concept.

Conditions are of 2 types logical AND (&&) and logical OR (||)

Logical AND (&&)

We use logical AND(&&) when all the conditions must be true to get a result.

Syntax:

if (condition1 && condition2) {

// Execution block

}

below is an implementation of a scenario where:

• A person aged greater than 18 years

            AND

• A person of sex female

will be eligible for a license.

if (age > 18 && sex === 'F') {
    grant_license = true;
}

Logical OR (||)

We use logical OR (||) when a minimum of one condition must be true to get a result.

Syntax:

if (condition1 || condition2) {

// Execution block

}

below is an implementation of a scenario where:

• A person aged greater than 60 years

   OR

• A person with a disability

will be eligible for a pension.

if (age > 60 || disability === true) { 
    allow_pension = true;
}

Combining both…

We can use a combination of both logical AND (&&) and logical OR (||) conditions. But it is suggested to use proper braces to make the conditions more meaningful.

Below is an implementation of a scenario where a bank will grant a loan to a customer only if the customer:

• Credit score greater than 600 and age is less than 50

 ( credit_score > 600 && age <50 ) 

 OR

• Has a valid source of income.
• Years of credit history greater than or equal to3
• Age must be between 25 to 45

 ( source_of_income === true && credit_history_yrs >= 3 && ( age >= 25 && age <=45 ) )

Combining both conditions:

if ( ( credit_score > 600 && age <50 ) || 
( source_of_income === true &&  credit_history_yrs >= 3 && ( age >= 25 && age <=45 ) ) ) {  
    grant_loan = true; 
}

Operator precedence

Remember, logical AND (&&) has higher precedence than logical OR (||). Hence, 

true || false && false // returns true, because && is executed first

(true || false) && false // returns false, because operator precedence defined using braces.