Custom filter prototype

array-prototype-filter.js

// Create our custom filter function and attach it to the prototype
Array.prototype.customFilter = function(callback) {
  const arr = this;
  const newArr = [];
  
  for(let i = 0; i < arr.length; i++) {
    if (callback(arr[i], i, arr)) newArr.push(arr[i]);
  }
  
  return newArr;
}

// Execute our custom filter function
const beachArr = ['waves', 'sharks', 'jellies', 'sand', 'pelicans'];
const newArr = beachArr.customFilter(item => item.length > 5);

// ['sharks', 'jellies', 'pelicans']
console.log(`Our newly filtered array: ${newArr}`);