# Falsy Bouncer Code Explanation

Hello,

I found the solution of Falsy Bouncer challenge but I don’t know how the code works. The code is simple. Below is the one given in the hint.

``````function bouncer(arr) {
return arr.filter(Boolean);
}
``````

Below is the one I found it myself but I don’t how it works too because I was just testing at that time.

``````function bouncer(arr) {
return arr.filter(function(x){ return x; });
}
``````

Could someone explain clearly how the 2 snippet code above works? For the second, why the falsy values are removed through the filter method even in the filter’s callback function there is no test case (just return x)?

Thank you.

Something like this:

• The function takes an argument called arr
• then it returns the result of a filter applied to each element of the array
• the result is returned as one array
• the filter only returns items that are `true`
• the filter checks the value of the item, lets say we have the array `[7, "ate", "", false, 9]` to check
• `7` is a number, but a number is not a Boolean. Hmm, we can’t compare apples to oranges, so let’ see what `7` is as a Boolean, because that is what we are interested in. `7` as a Boolean is `true` - oh, cool, since it is true we’ll add it to the result array.
• `ate` is a non-empty string = boolean `true` as well
• `""` is an empty string = boolean `false` here, let’s drop this from the result array
• `false` is , well, `false`. It will not be in the final array becasue, uhmm, it is `false`
• `9` is like `7` = `true`, the only number that is `false` is a `0` anyway

That is more or less how it goes.

ps. Javascript temporary makes items the same type for comparisons, so if you compare `"1" == 1` the result would be `true`. If you want to be very specific and tell Javascript to not convert the types you would have to use `===` as operator, but this is only really necessary in a very small number of cases, since most of the time type casting saves you a lot of work.

1 Like

This is called coercion and there is a great explanation in the YDKJS series here.

Thanks for the help Edited