How does the && operator work in javascript?

As javascript is a loosely-typed language, we can perform logical operations on any type.

1 && 2; 
null && undefined;
"hello" && true;

All the above operations are valid in javascript.

First, javascript decides whether an operand is truthy or falsy and, then it performs the logical operations on them.

A simple way to determine whether a value is truthy or falsy is by evaluating them in a boolean context.

if(value) { ... };
Boolean(value);

Syntax

Operand_1 && Operand_2 && Operand_3

Return Value

Starting from left, it returns the first operand that is false. If no operand evaluates to falsy value, it returns the last operand.

true && false && true;
// false

Let's consider the above example. The first falsy value we encounter is the second operand (false). Thus, the expression returns false.

{} && 0 && [];
// 0 

{} and [] are truthy values in javascript. So, the above expression returns the second operand(0).