var numbers = [12,15,12,13,50,46,50,25,1,3,7,64,125,25] ------------------ map formula -------------------------- //Map -Create a new array by doing something with each item in an array. // function namedouble(varibale) { // return varibale * 2; // } // const newNumbers = numbers.map(namedouble); const newNumbers = numbers.map(function (varibale) { return varibale * 2; }) // anonymus function because it does not have any name // var newNumbers = []; // numbers.forEach(function (varibale) { // newNumbers.push(varibale * 2); // }); console.log(newNumbers); ------------------ filter formula -------------------------- /Filter - Create a new array by keeping the items that return true. const newNumbers = numbers.filter(function(num) { return num < 10; }); // var newNumbers = []; // numbers.forEach(function(num) { // if (num < 10) { // newNumbers.push(num); // } // }) console.log(newNumbers); ------------------ reduce formula -------------------------- //Reduce - Accumulate a value by doing something to each item in an array. var newNumber = numbers.reduce(function (accumulator, currentNumber) { console.log("accumulator = " + accumulator); console.log("currentNumber = " + currentNumber); return accumulator + currentNumber; }); // var newNumber = 0; // numbers.forEach(function (currentNumber) { // newNumber += currentNumber // }) ------------------ find formula -------------------------- //Find - find the first item that matches from an array. const newNumber = numbers.find(function (num) { return num > 10; }) console.log(newNumber); ------------------ findindex formula -------------------------- //FindIndex - find the index of the first item that matches. const newNumber = numbers.findIndex(function (num) { return num > 10; }) console.log(newNumber);