JavaScript Comma Operator

JavaScript Comma Operator mainly evaluates its operands from left to right sequentially and returns the value of the rightmost operand.

let x = (1, 2, 3);
console.log(x); 

3

Here is another example to show that all expressions are actually executed.

let a = 1, b = 2, c = 3;

let res = (a++, b++, c++);

console.log(res);
console.log(a, b, c); 

3
2 3 4

Here is an example with function calls.

function Func1() {
    console.log('one');
    return 'one';
}
function Func2() {
    console.log('two');
    return 'two';
}
function Func3() {
    console.log('three');
    return 'three';
}

// Three expressions are
// given at one place
let x = (Func1(), Func2(), Func3());

console.log(x);

one
two
three
three

JavaScript Comma Operator – FAQs

What is the comma operator in JavaScript?

The comma operator allows multiple expressions to be evaluated in a single statement, returning the value of the last expression.

How does the comma operator work?

When the comma operator is used, each expression is evaluated from left to right, but only the result of the final expression is returned.

Where is the comma operator commonly used?

The comma operator is often used in for loops to include multiple expressions within the loop initialization or increment sections. It can also be used in variable assignments and other contexts where multiple operations need to be performed in sequence.

Can the comma operator be used in variable declarations?

Yes, the comma operator can be used to include multiple expressions in a single variable declaration statement, but only the last expression’s value will be assigned to the variable.

How does the comma operator compare to semicolons in JavaScript?

Semicolons separate statements, each of which is evaluated independently. The comma operator allows multiple expressions to be evaluated within a single statement, with only the last expression’s result being returned.

Can the comma operator be used in function arguments?

Yes, the comma operator can be used in function arguments to evaluate multiple expressions, but only the last expression’s value will be passed as the argument.

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Article Tags :

• JavaScript
• Web Technologies
• javascript-operators