Help Wanted: filter method on a prototype

JavaScript
1

Could someone help me a bit to understand the step by step of this please, whats actually filtering ? and whats the step by step process ?

Your code so far


// The global variable
var s = [23, 65, 98, 5];

Array.prototype.myFilter = function(callback){
// Only change code below this line
var newArray = [];
this.forEach(function(i) 
{if (callback(i)==true) 
newArray.push(i)
}
)
// Only change code above this line
return newArray;

};

var new_s = s.myFilter(function(item){
return item % 2 === 1;
});

console.log(new_s)

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.163 Safari/537.36.

Challenge: Implement the filter Method on a Prototype

Link to the challenge:

2

It explains about the Array.prototype.filter() method in the previous lesson.

3

The filter method on arrays allows you to create a new array made up of all elements from the original array that return a truthy value from a callback function.

// function that returns true when passed a positive number
const isPositive = x => x > 0;
// an array of numbers
const numbers = [-5, 4, -3, 2, -1, 0];
// Creates a new array of all positive numbers in `numbers`.
// This will pass each element from `numbers` to `isPositive`
// in order. If `isPositive` returns true, then the element is
// added to the new array assigned to `positives`.
const positives = numbers.filter(isPositive);

console.log(positives); // [4, 2]
4

i understand the filter method, the thing here is to make a filter without using the filter method, and im kinda lost on how this is working and whats actually the filtering condition

5

The filtering condition is the truthiness of the return value from callback.

1 Like
6

so, the actual condition is this function

(function(item){
return item % 2 === 1;
})

i guess is trying to filter odds from even (coz i saw the results) but not sure how x % 2===1 works hahah, something like if it can be divided by 2, i see it like if x % 2 is equal to 1

7

I was confused, I thought your question was about implementing a filter clone, but it was actually about the remainder operator %.

It returns the remainder from division. So as you surmised:

const isOdd = num => num % 2 === 1;
const isEven = num => num % 2 === 0;
1 Like
8

I was confused about it too, because i couldnt find the condition or atleast didnt make much sense to me. Thanks you very much for the help :smiley: