ECMAScript 6 Tutorial
In this video I’ll teach ECMAScript 6 in one video. In this video I’ll cover the vast majority of ECMAScript 6 in one video. We’ll cover Let, Constants, Data Types, Strings, Template Literals, Tagged Template Literals, For Of, Functions, Rest Parameters, Arrow Functions, Reduce, Filter, Map, Objects, Destructoring, Classes, Inheritance, Symbols, Arrays, Sets, Maps, forEach, Promises and more.
All of the code and a transcript of the video follows the video below.
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Cheat Sheet & Transcript
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---------- ecmascripttut.html ---------- <!doctype html> <html> <head> </head> <body> <script src="ecmatut.js"></script> </body> </html> ---------- ecmatut.js ---------- // ---------- LET ---------- if(true){ // If you use var then the variable is available // globally versus let which makes the variable // available only in the block // let x = 10; var x = 10; document.write("x = " + x + "<br />"); } // x is undefined here document.write("x = " + x + "<br />"); // If you use let in a block with the same name // it won't effect the value outside of the block var y = 10 if(true){ let y = 20 } document.write("y = " + y + "<br />"); // ---------- CONST ---------- // You can define constant values that can't change const PI = 3.14159 // This throws an error // PI = 2.13 // This won't since the constant is in a block if(true){ const PI = 2.13 } // ---------- DATA TYPES ---------- // You still don't declare a data type, but instead // the value defined defines the type being Boolean, // Number, String, Object, Symbol document.write(typeof true + "<br />"); document.write(typeof 3.14 + "<br />"); document.write(typeof "string" + "<br />"); document.write(typeof Symbol() + "<br />"); document.write(typeof {a:1} + "<br />"); document.write(typeof [1,2,3] + "<br />"); document.write(typeof undefined + "<br />"); // ---------- STRINGS ---------- // You can use string interpolation using template // literals let fName = "Derek"; let lName = "Banas"; document.write(`${fName} ${lName}` + "<br />"); // Calculation in output using template literals let num1 = 10 let num2 = 5 document.write(`10 * 5 = ${num1 * num2}` + "<br />"); // You can use tagged template literals to modify // output using a function // The strings array contains the strings and the // values array the substitutions function doMath(strings, ...values) { if (strings[0] == 'Add'){ document.write(`${values[0]} + ${values[1]} = ${values[0] + values[1]} <br />`); } else if (strings[0] == 'Sub'){ document.write(`${values[0]} - ${values[1]} = ${values[0] - values[1]} <br />`); } } doMath`Add${10} ${20}`; doMath`Sub${10} ${20}`; // Iterate over characters for(let c of fName){ document.write(`${c} <br />`); } // Repeat a string document.write("Hello ".repeat(3) + "<br />"); // Does a string start with a value document.write(fName.startsWith("De") + "<br />"); // Does it end with document.write(fName.endsWith("ek") + "<br />"); // Does it include document.write(fName.includes("ere") + "<br />"); // Multiline strings let multilineStr = "This is \ a multiline \ string"; document.write(`${multilineStr} <br />`); let anothermlstr = `Another multiline string`; document.write(`${anothermlstr} <br />`); // ---------- FUNCTIONS ---------- // Default values are defined next to parameters function getSum(num1 = 1, num2 = 1){ document.write(`${num1} + ${num2} = ${num1+num2}<br />`); // arguments[] only receives the value passed document.write(`${arguments[0]} + ${arguments[1]}<br />`) } getSum(3); // Rest parameters, which are preceeded by ... // become an array // You can only have 1 rest parameter and it must // be defined last function getSumMore(...vals){ let sum = 0; for(let i = 0, len = vals.length; i < len; i++){ sum += vals[i]; } document.write(`The sum is ${sum}<br />`); } getSumMore(1,2,3,4); // You can also pass arrays let vals = [1,2,3,4,5]; getSumMore(...vals); // Arrow functions define parameters followed // by the body of the function let difference = (num1, num2) => num1 - num2; document.write(`5 - 10 = ${difference(5,10)}<br />`); // They can contain more then 1 statement let mult = (num1, num2) => { let product = num1 * num2; document.write(`${num1} * ${num2} = ${product}<br />`); }; mult(5,50); // You can use arrow functions with map, filter and // map let valArr = [1,2,3,4,5]; // Reduce applies a function against an accumulator // to get a single result let sumVals = valArr.reduce((a, b) => a + b); document.write(`Sum : ${sumVals}<br />`); // Filter returns those values that pass the condition let evens = valArr.filter(v => v % 2 == 0); document.write(`Evens : ${evens}<br />`); // Map performs the given action on every item passed let doubles = valArr.map(v => v * 2); document.write(`Doubles : ${doubles}<br />`); // ---------- OBJECTS ---------- // You create object literals like this function createAnimal(name, owner){ return { // Properties name, owner, // Create a method getInfo(){ return `${this.name} is owned by ${this.owner}` }, // Objects can contain other objects address: { street: '123 Main St', city: 'Pittsburgh' } }; } var spot = createAnimal("Spot", "Doug"); // Execute method document.write(`${spot.getInfo()}<br />`); // Access object in the object document.write(`${spot.name} is at ${spot.address.street}<br />`); // Get properties and methods of object document.write(`${Object.getOwnPropertyNames(spot).join(" ")} <br />`); // You can store values from Objects with destructoring let { name, owner } = spot; document.write(`Name : ${name}<br />`); // Get the inner class value let { address } = spot document.write(`Address : ${address.street}<br />`); // You can destructor arrays as well let favNums = [2.718, .5772, 4.6692]; let [,,chaos] = favNums; document.write(`Chaos : ${chaos}<br />`); // You can use rest items to grab part of an array let [, ...last2] = favNums; document.write(`2nd Num : ${last2[0]}<br />`); // This can be used to switch values let val1 = 1, val2 = 2; [val1,val2] = [val2,val1]; document.write(`Val2 : ${val2}<br />`); // ---------- CLASSES ---------- // Classes now work much like they do in other languages class Mammal{ constructor(name){ this._name = name; } // Getter get name() { return this._name; } // Setter set name(name){ this._name = name; } // Static Mammal creator static makeMammal(name){ return new Mammal(name); } getInfo(){ return `${this.name} is a mammal`; } } // Create an object let monkey = new Mammal("Fred"); // Change name monkey.name = "Mark"; // Call getter document.write(`Mammal : ${monkey.name}<br />`); // Create Mammal using static function let chipmunk = Mammal.makeMammal("Chipper"); document.write(`Mammal 2 : ${chipmunk.name}<br />`); // You can inherit properties and methods with extends class Marsupial extends Mammal{ constructor(name, hasPouch){ // Call the super class constructor super(name); this._hasPouch = hasPouch; } get hasPouch() { return this._hasPouch; } set hasPouch(hasPouch){ this._hasPouch = hasPouch; } // You can override methods getInfo(){ return `${this.name} is a marsupial`; } } let kangaroo = new Marsupial("Paul", true); document.write(`It is ${kangaroo.hasPouch} that ${kangaroo.name} has a pouch<br />`); // Test overridden method document.write(`${chipmunk.getInfo()}<br />`); document.write(`${kangaroo.getInfo()}<br />`); // You can dynamically inherit from Classes function getClass(classType){ if (classType == 1) { return Mammal; } else { return Marsupial; } } class Koala extends getClass(2){ constructor(name){ super(name); } } let carl = new Koala("Carl"); document.write(`${carl.getInfo()}<br />`); // ---------- SYMBOLS ---------- // A Symbol is like an enumerated type that can be used as // identifiers and they can't be changed (immutable). // Create a symbol that is used like a label in an array // You can provide a description in quotes let capital = Symbol("State Capital"); let pennsylvania = {}; pennsylvania[capital] = "Harrisburg"; document.write(`Capital of PA : ${pennsylvania[capital]}<br />`); // Get the description document.write(`Symbol Capital : ${capital.toString()}<br />`); // You can share symbols by using symbol.for() let employNum = Symbol.for("Employee Number"); let bobSmith = {}; bobSmith[employNum] = 10; let sallyMarks = {}; sallyMarks[employNum] = 11; document.write(`Bob : ${bobSmith[employNum]}<br />`); document.write(`Sally : ${sallyMarks[employNum]}<br />`); // ---------- ARRAYS ---------- // Array.of() is used to create arrays instead of the array // constructor let array1 = Array.of(1,2,3); // Create an object into an array let array2 = Array.from("word"); // You can use Array.from to manipulate values let array3 = Array.from(array1, (value) => value * 2); // Iterate over values for (let val of array3) document.write(`Array Val : ${val}<br />`); // ---------- SETS ---------- // A Set is a list of values with no duplicates var randSet = new Set(); randSet.add(10); randSet.add("Word"); // Check to see if set contains a value document.write(`Has 10 : ${randSet.has(10)}<br />`); // Get size of Set document.write(`Set Size : ${randSet.size}<br />`); // Delete item from list randSet.delete(10); // Iterate a Set for (let val of randSet) document.write(`Set Val : ${val}<br />`); // ---------- MAPS ---------- // A Map is a collection of key/value pairs var randMap = new Map(); randMap.set("key1", "Random String"); randMap.set("key2", 10); // Get values document.write(`key1 : ${randMap.get("key1")}<br />`); document.write(`key2 : ${randMap.get("key2")}<br />`); // Get size document.write(`Map Size : ${randMap.size}<br />`); // Iterate Map randMap.forEach(function(value, key){ document.write(`${key} : ${value}<br />`); }); // ---------- PROMISES ---------- // Promises define code that is to be executed later // Promises either succeed or fail once // They either are fulfilled, rejected, pending, or settled // A Promise that is handled immediately var p1 = Promise.resolve('Resolve Me'); // then takes 2 optional arguments being first a callback // for a success and another for failure p1.then((res) => document.write(`${res}<br />`)); // Create a promise that executes after 2 seconds var p2 = new Promise(function(resolve, reject){ setTimeout(() => resolve('Resolve Me'), 2000); }); p2.then((res) => document.write(`${res}<br />`)); // Here I demonstrate how then is used if a promise is // fulfilled or rejected let randVal = 18; var p3 = new Promise(function(resolve, reject){ if (randVal == 6){ resolve("Good Value"); } else { reject("Bad Value"); } }); p3.then((val) => document.write(`${val}<br />`), (err) => document.write(`${err}<br />`)); // You should add catch to a chain to handle errors var p4 = new Promise((resolve, reject) => { if (randVal <= 17){ throw new Error("Can't Vote"); // Same as a Reject } else { resolve("Can Vote"); } }); p4.then((val) => document.write(`${val}<br />`)) .catch((err) => document.write(`${err.message}<br />`)); |
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