selfFilter.js

const selfFilter = function (fn, context) {
    let arr = Array.prototype.slice.call(this)
    let filteredArr = []
    for (let i = 0; i < arr.length; i++) {
        if(!arr.hasOwnProperty(i)) continue;
         fn.call(context, arr[i], i, this) && filteredArr.push(arr[i])
    }
    return filteredArr
}

Array.prototype.selfFilter = selfFilter;