SOURCE

const arr = [1,2,3,4,5]

Array.prototype.filter = function(cb, ctx) {
    let i = 0
    let result = []
    while (i <= this.length) {
        if(cb.call(ctx || this, this[i], i, this)) {
            result.push(this[i])
        }
    }

    return result
}

const filters = arr.filter((val, key, arr) => {
    return val > 3
})

console.log(filters)