AI solution for JavaScript Quiz on BFE.dev
46. Implicit Coercion IV

The code below outputs false.

Explanation:

In JavaScript, when comparing values of different data types with the double equals == operator, coercion occurs. It means if the operands are not of the same type, JavaScript will try to convert one type to match the other type.

In this code, foo is an array with one element 0. When we compare foo with true, JavaScript will try to convert true to a number. Notice that the element 0 has falsy value in JavaScript, which means when coerced to a boolean, it is converted to false. Therefore, foo == true becomes 0 == 1, which returns false.

Similarly, when we compare foo with false, JavaScript will try to convert false to a number, which equals 0. Thus, foo == false actually becomes 0 == 0, which returns true. However, the condition in the if statement is if (foo), which evaluates to true because foo is not an empty array or null or undefined. Therefore, the code executes the first branch, and false is printed to the console.