# Learned Array with Bus and Passengers.. An array is a simple group or list of basic data types (String, Number, boolean, array, and object or null and undefined ). Array items could be a single datatype of all of them ex: \["String", 4, true, \["another", "list", "of", "data"\], {name:"chaiCode"}\] Here we learn javascript arrays with a simple example of bus and passengers with #chaicode ## .length .length is used to get the total element count. `let bus = ["0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0", "0"]` `bus.length // 13 returns the array length ( count of items the array is 5)` ## .at() and .indexOf() .at() and .indexOf are used to the passenger `let bus2 = ["driver","hitesh","piyush","anirudh","main bhi hu"]` [`bus2.at`](http://bus2.at)`(3) // return anirudh it start from the 0 (doesn't include drive seat only passengers)` `bus.indexOf("main bhi hu") // Return 4 position of the the value and starts with 0` ## .fill() and .concat() .fill(1): Fill all the seats with 1 passenger .concat(): add another bus passenger to your bus `bus3 = bus.fill(1) // update all values with 1` `bus3 = bus2.concat(bus) //add new array with the old array` ## .push() and .pop() add and remove items at ends of the array(list) .push() // board new passenger from the back gate .pop() // deboard passenger from the back gate `bus4 = bus.push('gents'); // gents boarded bus from back gate` `bus4 = bus.pop('gents'); // after destination gents deboarded bus from back gate` ## .unshift() and .shift() add and remove items at the start of the array(list) .unshift() // boarded ladies passengers from front gate .shift() // deboarded ladies passengers from front gate ## .find(), .some(), .every(), .includes(), and .filter() some other important methods of arrays .find() // check for any lady passenger by name .some() // check for any lady passenger by boolean .every() // check for all passenger is women .include() // any lady passenger by name .filter() // give me the ladies passenger list `let ticketPrize = [5,7,10,15,20,30,40,60,80]` `ticketPrize.find(item => item === 10) // return 10 the value if true` `ticketPrize.some(item => item < 10) // return true beacuse of value 5 is lesser` `ticketPrize.every(item => item < 10) // return false beacause of other value is higher` `ticketPrize.includes(5) // return true because 5 is in the list` `ticketPrize.filter(item => item <= 9) // [5, 7] retrun the value` `const passengers = [` `{ name: 'Driver', gender: "M", ticket: false },` `{ name: 'Conductor', gender: "M", ticket: false },` `{ name: 'Divya', gender: "F", ticket: true },` `{ name: 'Kavya', gender: "F", ticket: true },` `{ name: 'Sandya', gender: "F", ticket: true },` `{ name: 'Vandya', gender: "F", ticket: true },` `{ name: 'Hitesh', gender: "M", ticket: true },` `{ name: 'Piyush', gender: "M", ticket: true },` `{ name: 'Anirudh', gender: "M", ticket: false },` `{ name: 'Jagdamba', gender: "M", ticket: true },` `{ name: 'Dubey', gender: "M", ticket: true }` `];` `passengers.find(item => item.gender==="F"); // return the Divya details first F gender passenger` `assengers.some(item => item.gender==="F"); // return TRUE bacause of some passengers gender are F` `assengers.every(item => item.gender==="F"); // return FALSE because not every passengers gender is F` `assengers.filter(item => item.ticket === false); return list of ticket false list` ## .map(), .flat() and .flatMap() .map(): used for any performance with each element ticketPrize = \[5,7,10,15,20,30,40,60,80\] dobledPrize = [ticketPrize.map](http://ticketPrize.map)(prize => prize \* 2) // new array with doubled prize .flat(): used for combining multiple arrays into a single array `staff = ["dirver", "conductor"]` `ladies = ["Divya","Kavya","Sita","Geeta"]` `gents = ["Hitesh","Piyush","Jagdamba","Dubey"]` `bus = [staff, ladies, gents].flat(); // get all value in one` bus = \[staff, ladies, gents\].flatMap(p => p + ' in the bus'); // get all value in one ## .split() and .join() .split() used for creating array let myFriends = "Hitesh,Piyush,Jagdamba,Dubey" `frinedArr = myFriends.split(','); // create element on the based of ,` .join() is used for array to string `names = frinedArr.join(',') // array convert back to string` ## .slice() and .splice() .slice() this is used to slice the list bus Doesn't modify the original array and returns a new array with selected elements like: ticket done for some passenger some are pending but all are in the bus `let bus7 = ["driver","conductor","Hitesh","Piyush","Jags","Students"]` `bus7.slice(2) // first 2 dirver and conductor does not require tickets` `bus7.slice(2,5) // first 2 and after and after 5 (dirver and conductor and stundents and so not required)` .splice() Modifies the original array and returns removed elements like: some of the passengers deboarded the bus but some still in the bus `let bus8 = ["driver","conductor","Hitesh","Piyush","Jags","Students"]` `busSplice = bus8.splice(2) // store only passengers and bus8 has only dirver and conductor` `busSplice = bus8.splice(2,3) // first value start from and second value count of delete/splice` ## .reduce() reduce is used for some calculations with all elements. like the total collection of bus tickets. `let ticketSold = [10,15,20,30,40,50,5];` `let totalSold = ticketSold.reduce((total,perticket) => total + perticket,0); //returns 170` ## Surprise Mee surprise is that you can create your methods and surprise anyone which called polyfill lets create I need to add the text "ticket kat gaya" for all bus passengers for tickets `Array.prototype.ticketDone = function(mes){ let pList = []; for(let i = 0; i < this.length; i++){ pList.push(mes(this[i])); } return pList; }` `let bus = ["p1","p2","p3","p4","p5","p6","p7","p8"]` `bus.ticketDone(pas => pas + " ticket kat gaya");` ## Conclusion + Revision `const myArr = [1,2,3,4,5.5] myArr.length() // returns the array length ( count of items the array is 5)` [`myArr.at`](http://myArr.at)`(n) // get the value of nth position ( 4th position value is 5.5)` `myArr.indexOf(4) // get the position of value (5 is at 4th position)` `myArr.concat(4,[45,56,76,86]) // add more value into the array (also can be single value or can be another array itself)` `myArr.fill(0); // fill all the position with passed value` `myArr.find((item) => item < 7) // check for the first item to match the condition` `myArr.some((item) => item < 7) // check for the some item to match the condition` `myArr.every((item) => item < 7) // check for all items to match the contions with iterations with true and false` `myArr.includes(item); // return booleans if item avilable or not in the array` `myArr.filter((item) => item >4) // return the list of the array with matched the conditions` [`m`](http://myArr.map) `myArr.map(item => item * 2) // return the new array with any actions performed with each elements` `myArr.flat(); // convert in the single array from multilevel array` `myArr.flatMap(item => item + "a") // maping and also flat the array if there is multilevel array` `myArr.join('-') // return string with all value differnciate with mentioned value` `myArr.split('-') // return array with split value myArr.push(7) // add new item in the last of the array myArr.pop // removed and returns the last item of the array` `myArr.unshift(0) // add new item or items in the start of array` `myArr.shift() // removed first item from array` `myArr.splice(start, count) // returns removed form old array and return the new array from start to number of counts` `myArr.slice(count) // just slice removed or sliced from start to count` `arr.reduce((total,item) => total+item,intial) // return the sum of the array with intial if added` Polyfill to create your custom methods `Array.prototype.myMap = function(fn){` `myArr = []` `for(let i=0; i