Map(), Filter(), Every(), Some(), Reduce() are your best friends!

Map(), Filter(), Every(), Some(), and Reduce() are your best friends when it comes to processing data in JavaScript. They can help you transform data, select specific items from a dataset, and check for conditions. Map(), Filter(), Every(), Some(), and Reduce() are all methods of the Array prototype, so they can be used on any array. To use Map(), Filter(), Every(), Some(), or Reduce() on an array, you simply call the method on the array, passing in the appropriate arguments. Map() and Filter() take a callback function as their first argument. Every() and Some() take a callback function as their only argument. Reduce() takes a callback function as its first argument and an optional initial value as its second argument. Callback functions are just regular functions that are called for each element in the array.
Here's a quick overview of how each method works:

Array.prototype.map()

The map() method transforms an array by invoking a callback function on each element in the array. The return value of the callback function is used to populate a new array, which is returned by map().

let arr = [2, 3, 4, 5, 6];
let modifiedArr = arr.map(function(element){
    return element *3;
});
console.log(modifiedArr); // [6, 9, 12, 15, 18]

Array.prototype.filter()

The filter() method filters an array by invoking a callback function on each element in the array. If the callback function returns true, the element is included in the new array that filter() returns.

let numbers = [1, 3, 6, 7, 8, 11];
let greaterThanSix = numbers.filter(function(number) {
  return number > 6;
});
console.log(greaterThanSix ); // [7, 8, 11]

Array.prototype.every()

The every() method checks if all elements in an array pass a test implemented by a callback function. If all elements pass the test, every() returns true; otherwise, it returns false.

const isBelowThreshold = (currentValue) => currentValue < 40;
const array1 = [1, 30, 39, 29, 10, 13];
console.log(array1.every(isBelowThreshold)); //  true

Array.prototype.some()

The some() method checks if at least one element in an array passes a test implemented by a callback function. If at least one element passes the test, some() returns true; otherwise, it returns false.

const arr1 = [2, 5, 8, 1, 4];
const arr2 = [12, 5, 8, 1, 4];
function isBiggerThan10(element, index, array) {
  return element > 10;
}
console.log(arr1.some(isBiggerThan10));  // false
console.log(arr2.some(isBiggerThan10)); // true

Array.prototype.reduce()

The reduce() method reduces an array to a single value by invoking a callback function on each element in the array and using the return value of the callback function as the next value in the reduction. The return value of reduce() is the final reduced value.

const array1 = [1, 2, 3, 5];
// 0 + 1 + 2 + 3 + 5
const initialValue = 0; 
const sumWithInitial = array1.reduce(
  function(previousValue, currentValue) {
    const initialValue = previousValue + currentValue; 
    return initialValue;
  }  
);
console.log(sumWithInitial); // 11

So, next time you're working with data in JavaScript, don't forget about Map(), Filter(), Every(), Some(), and Reduce(). They just might be your best friends!