Question

In the below code how does passing bar as

 function (n) { return n; } 

to foo evaluate to true in the if block?

 function foo(bar) {

    if (bar) {
       // true
    } else {
       // false
    }
 }

This has me puzzled so any help is much appreciated.

Answer 1

If bar is bound to an anonymous function, then it is an object. Objects are ‘truthy’ in JavaScript.

The only values in JavaScript that are ‘falsy’ are:

• false
• null
• undefined
• '' (empty string)
• 0 (zero as a number)
• NaN

Everything else is ‘truthy’, including function objects.

If you meant to call the anonymous function, you’d do if (bar(5)) which would call your anonymous function with the argument 5. Then your anonymous function would return n (which is 5 in this case). As 5 is not a falsy object, this would go to the true branch as well. Doing if (bar(0)) would got to the else branch, because 0 is falsy.