2634. Filter Elements from Array
Easy
315
22

Given an integer array `arr` and a filtering function `fn`, return a filtered array `filteredArr`.

The `fn` function takes one or two arguments:

• `arr[i]` - number from the `arr`
• `i` - index of `arr[i]`

`filteredArr` should only contain the elements from the `arr` for which the expression `fn(arr[i], i)` evaluates to a truthy value. A truthy value is a value where `Boolean(value)` returns `true`.

Please solve it without the built-in Array.filter method.

Example 1:

```Input: arr = [0,10,20,30], fn = function greaterThan10(n) { return n > 10; }
Output: [20,30]
Explanation:
const newArray = filter(arr, fn); // [20, 30]
The function filters out values that are not greater than 10```

Example 2:

```Input: arr = [1,2,3], fn = function firstIndex(n, i) { return i === 0; }
Output: 
Explanation:
fn can also accept the index of each element
In this case, the function removes elements not at index 0
```

Example 3:

```Input: arr = [-2,-1,0,1,2], fn = function plusOne(n) { return n + 1 }
Output: [-2,0,1,2]
Explanation:
Falsey values such as 0 should be filtered out
```

Constraints:

• `0 <= arr.length <= 1000`
• `-109 <= arr[i] <= 109`
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