function bouncer(arr) {
// Don't show a false ID to this bouncer.
function a(b) {
if(b !== false) {
return b;
}
}
arr = arr.filter(a);
return arr;
}
bouncer([7, 'ate', '', false, 9]);
I have to return true boolean statements only, and when I run this code, it works. However, I am quite confused because my "if statement" will work whether it's b !== true or b !== false. Could someone please explain the reason why this works both ways?
Apparently .filter() was introduced in ES5.
This definitely helped me wrap my mind around what's going on here. Hope it helps!
Essentially, writing:
arr.filter(Boolean)
is the same as writing:
arr.filter( function(x) { return Boolean(x); });
since Boolean() is also a function that returns truthy when true and falsy when false!
Example:
var a = [1, 2, "b", 0, {}, "", NaN, 3, undefined, null, 5];
var b = a.filter(Boolean); // [1, 2, "b", {}, 3, 5];
Source: here.
I was solving a similar problem and came up with this:
function bouncer(arr) {
return arr.filter(Boolean);
}
console.log(bouncer([7, 'ate', '', false, 9]));
simplest way to do it :
function bouncer(arr) {
return arr.filter(x => !!x);
}
It's because you return the value. The filter function should return true or false like this:
function bouncer(arr) {
arr = arr.filter(function(x) { console.log(x === true)
if(x !== false) {
return true;
}
});
return arr;
}
or shorter:
function bouncer(arr) {
return arr.filter(function(x) { console.log(x === true)
return x !== false;
});
}
Your function acts is it does because JavaScript values in boolean comparisons are "truthy" or "falsey". Non-booleans are coerced to a boolean value when used in a boolean context (comparisons, if statements, etc.)
If I understand your intent, you can modify your function to get your expected output like this:
function bouncer(arr) {
// Don't show a false ID to this bouncer.
function a(b) {
if(typeof(b) === 'boolean' && !b) {
return new Boolean(b);
}
}
arr = arr.filter(a);
return arr;
}
bouncer([7, 'ate', '', false, 9, true]);
I came across this exercise and was playing about with it somewhat. It ended up helping me understand it a bit better, so if you may I will add a bit of clarity to this bouncer function.
function bouncerOne(array){
let truthy = array.filter(x => x);
// This takes the .filter() and applies the anon function where it takes
// the value and returns the positive value. All values that are not Falsy including
// objects and functions would return True.
console.log("The Truth is:", truthy);//this Outputs the result to the console.
let falsy = array.filter(x => !x);
//This takes the .filer() and applies the
//annon function where it takes the value and only returns items that ARE NOT True.
//So Falsy Values are taken.
console.log("The Falsy Values are",falsy);
//The annon function of (x => x) & (x => !x)
// really makes use of the strict equality power of JavaScript.
// Where simple conditional test can be carried out.
};
console.log(bouncerOne([7, "ate", "", false, 9,null,42,"Bingo",undefined,NaN]));
//Returns: The Truth is: [ 7, 'ate', 9, 42, 'Bingo' ]
//The Falsy Values are [ '', false, null, undefined, NaN ]
Double Not operator ( !! ) convert value into Boolean form. eg : !!true // true;
let a = [1, 2, "b", 0, {}, "", NaN, 3, undefined, null, 5];
// writing in ES6 syntax
a.filter(v=>!!v); // [1, 2, 'b', {…}, 3, 5]
// writing with function keyword
a.filter( function(v) { return (!!v); }); // [1, 2, 'b', {…}, 3, 5]
So basically, your if statement is not doing anything in this code because it is not changing arr which you are returning as output. If you set b!== true or false it has no effect. Even if you remove the "if statement", you will get same answer.
