Why is output equal 2?

Question

https://code.sololearn.com/WW1OMOteApPb/?ref=app

Answer 1

Array <b> contains even elements filtered from array <c>, if you want you can log <b> in console, it contains 2 and 4.

Answer 2

Ipang, please, can you explain and show how it works?

Answer 3

I don't understand

Answer 4

Ipang, if we remove "-1", then we get a uneven number?
https://code.sololearn.com/Wan203cC14qV/?ref=app

Answer 5

Ipang, can I make it easier this way?
https://code.sololearn.com/Wwx5YR3mu5G3/?ref=app

Answer 6

* Create new array <c> containing 4 elements (1, 2, 3, 4)
var c = new Array(1,2,3, 4);

* Filter even numbers from array <c> into another array <c> using `filter` method of Array class.
var b = c.filter (function (a) {
return (a % 2 - 1);
});

* To understand how `filter` method works please read this page 👇
// https://codeburst.io/useful-javascript-array-and-object-methods-6c7971d93230

* Display an alert dialog showing the first element of array <b>.
alert(b[0]);

* To see the whole array <b> do this instead.
alert(b);

Answer 7

Yes, the `filter` method uses a predicate function, which accepts an argument (each of the array's elements). And the function is expected to return a boolean-like value (0 = false, other values = true). The value returned by the predicate function decides whether an element should be included in the filter result.

`filter` method pass each array element as argument for the predicate function, one by one. If the predicate function returns true, the element given as argument will be included in the result. Otherwise, the element will not be included in the result (array <b>).

Answer 8

Now let's see what happens in the predicate function with array <c> content [ 1, 2, 3, 4 ]

<a> = 1
1 % 2 yields 1, subtract by one => 0 means return false (1 will be excluded from result)

<a> = 2
2 % 2 yields 0, subtract by one => -1 means return true (2 will be included in result)

<a> = 3
3 % 2 yields 1, subtract by one => 0 means return false (3 will excluded from result)

<a> = 4
4 % 2 yields 0, subtract by one => -1 means return true (4 will included in result)

Answer 9

Yes, that can do as well 👍

Answer 10

i don’t know much about algebra, but i know 1 + 1 = 2!!!!!