JavaScript

Repeat the same work

1. 20A quick recapBring variables and branching back to mind before we start the new chapter.4 slides · 13 exercisesGo to the exercises
2. 21Repeating with whileGet the same work done over and over, for as long as a condition holds.6 slides · 13 exercisesGo to the exercises
3. 22Repeating with forLearn the other way of writing a loop, with the start, the condition and the update all on one line.6 slides · 13 exercisesGo to the exercises
4. 23Choosing between the two loopsGet a feel for how to decide whether to reach for while or for.4 slides · 13 exercisesGo to the exercises

Line values up in an array

1. 24Holding values together in an arrayLearn how to keep several values together in a single container.4 slides · 13 exercisesGo to the exercises
2. 25Taking one item out of an arrayName a position and take a single value out of the array.4 slides · 13 exercisesGo to the exercises
3. 26Changing what is in an arrayName a position and swap an item out for something else.4 slides · 13 exercisesGo to the exercises
4. 27Working through an array with a loopStep the number up one at a time and handle the items in order.5 slides · 13 exercisesGo to the exercises
5. 28Using the length of an arrayTake the number of items with .length and let the array decide the number of laps.4 slides · 13 exercisesGo to the exercises

Hold values by name with objects

1. 29Holding values by name with an objectLearn the other way of holding data — gathering information up as name and value pairs.4 slides · 13 exercisesGo to the exercises
2. 30Reading and writing propertiesName a property to take its value, change it, or add a new one later on.4 slides · 13 exercisesGo to the exercises
3. 31Putting objects in an arrayLine objects of the same shape up in an array and reach values out of the nesting.4 slides · 13 exercisesGo to the exercises
4. 32Running a loop over the nestingPut a for over an array of objects to list them out and add them up.4 slides · 13 exercisesGo to the exercises

When there is no value

1. 33Peeking at a value that is not thereMeet undefined, the value you get back when you ask for a number or a property that does not exist.4 slides · 13 exercisesGo to the exercises
2. 34Checking for undefined and stepping around itSpot the case where there is no value with a branch, and switch to a different display or a different route.5 slides · 13 exercisesGo to the exercises

Put it together

1. 35Putting the chapter togetherCombined practice using arrays, objects, loops and branching together. As a round-up there are no basics — just the ten practice questions.3 slides · 10 exercisesGo to the exercises
2. 36Tidying up the outputCombined practice on headings, numbers, separators and units, to finish with output people can read. As a round-up there are no basics — just the ten practice questions.3 slides · 10 exercisesGo to the exercises

More combined practice

1. 37Putting for and arrays togetherLearn the single most important pattern there is: working through every item of an array with a for loop.5 slides · 13 exercisesGo to the exercises
2. 38Putting for, if and arrays togetherGet to where you can handle "only the items that match" out of the whole lot.5 slides · 13 exercisesGo to the exercises
3. 39Putting for, if-else and arrays togetherGet to where you can send every item down "one way or the other".6 slides · 13 exercisesGo to the exercises
4. 40Putting for, if-else if and arrays togetherTake on the culminating pattern: sorting every item into three or more groups.6 slides · 13 exercisesGo to the exercises

Write a function and call it

1. 41Giving work a nameGather some work into one lump so that you can call it up by name.5 slides · 13 exercisesGo to the exercises
2. 42Putting a function in a variableA function is a value too. Learn the way of writing that puts one in a variable first.4 slides · 13 exercisesGo to the exercises
3. 43Writing it short with an arrow functionUse => to write a function expression in a much shorter form.4 slides · 13 exercisesGo to the exercises

Pass values in as arguments

1. 44Handing a value to a functionHand a value in inside the brackets and make a function whose result changes every time you call it.5 slides · 13 exercisesGo to the exercises
2. 45Catching more than one valueHand over several values separated by , and catch them in the order you wrote them.5 slides · 13 exercisesGo to the exercises

Send a return value back

1. 46Sending a result back out of a functionSend a result back with return and catch it where you called from.5 slides · 13 exercisesGo to the exercises
2. 47Using a return value where it standsDrop a return value straight into a condition or a sum without putting it in a variable.4 slides · 13 exercisesGo to the exercises

Where a variable is visible

1. 48How far a variable reachesGet straight how far a variable made inside a function can be seen.5 slides · 13 exercisesGo to the exercises

Put it together

1. 49Pulling functions togetherA round-up of exercises solved by combining functions, parameters, return values and scope. Being a round-up, there are no three basics — just ten to practise on.3 slides · 10 exercisesGo to the exercises

The blueprint and the real thing

1. 50Objects, one more timeRemember the shape that holds information as name-and-value pairs. No new grammar here; this one is for getting the feel back.4 slides · 13 exercisesGo to the exercises
2. 51A class is a blueprint for one shapeMeet the thinking and the writing behind the class, the blueprint for turning out objects of the same shape.4 slides · 13 exercisesGo to the exercises
3. 52Making a real one from the blueprintBring a real one into being from a blueprint with new, give it properties and read them back. That real one is called an instance.4 slides · 13 exercisesGo to the exercises

Set values up as you create

1. 53Work that runs by itself as you make oneSee for yourself how a constructor written inside a class runs by itself every time you new.4 slides · 13 exercisesGo to the exercises
2. 54Giving it contents with thisWrite this.name = value inside the constructor and have the properties ready the moment it is made.4 slides · 13 exercisesGo to the exercises
3. 55Handing values over as you make oneHave the constructor catch arguments and give each real one different contents.5 slides · 13 exercisesGo to the exercises

Give it behaviour

1. 56Giving a class something it can doCall a method — a function written inside a class — from an instance.4 slides · 13 exercisesGo to the exercises
2. 57Looking at your own contents from a methodWrite this.property inside a method and use the values held by the very thing it was called on.4 slides · 13 exercisesGo to the exercises
3. 58Calling one method from anotherWrite this.otherMethod() inside a method and put pieces of work together.4 slides · 13 exercisesGo to the exercises

Inherit, then change what differs

1. 59Building on a class you already haveUse extends to make a new class that takes over the contents of one you already have.4 slides · 13 exercisesGo to the exercises
2. 60Using what you took overCall a method written on the parent class from an instance of the child class.6 slides · 13 exercisesGo to the exercises
3. 61Adding something the child alone can doWrite a method of its own on the child class and give it behaviour the parent does not have.4 slides · 13 exercisesGo to the exercises
4. 62Swapping out behaviour you took overRewrite a method of the same name on the child and change the behaviour for that child alone.4 slides · 13 exercisesGo to the exercises
5. 63Calling the parent's work, then adding to itUse super() when you rewrite a constructor on the child, and super.method() to call the parent's method.5 slides · 13 exercisesGo to the exercises

Split files and join them back

1. 64When one file gets fatSee where it hurts to keep writing everything in one place, and try cutting it up by what each part does.5 slides · 13 exercisesGo to the exercises
2. 65Split the files and join them upSend things out with export default and pull them in with import. Learn the smallest shape that joins two files.5 slides · 13 exercisesGo to the exercises
3. 66Sending values out of a fileNot only functions — strings, arrays and objects go out with export default too. Try putting data in its own file.5 slides · 13 exercisesGo to the exercises
4. 67Send out several, each with a namePublish more than one thing from a single file, and pull in only what you need with { }.6 slides · 13 exercisesGo to the exercises
5. 68Pointing at where a file isGet hold of what ./ and ../ mean, so files sorted into folders can be joined up too.5 slides · 13 exercisesGo to the exercises

Use parts that already exist

1. 69Borrowing code someone else wroteMeet the idea of pulling in ready-made code as a package, and see how you would get hold of one.6 slides · 13 exercisesGo to the exercises
2. 70Calling what a package offersPull in functions a package published by name, and put their return values together.5 slides · 13 exercisesGo to the exercises

Array methods

1. 71Adding to the back of an arrayUse the push method so you can add an item to the end of an array.5 slides · 13 exercisesGo to the exercises
2. 72Doing the same thing to every itemHand a function to the forEach method and deliver the same work to every item of an array.6 slides · 13 exercisesGo to the exercises
3. 73Finding the one that matchesHand a condition function to the find method and take out the first item that matches.5 slides · 13 exercisesGo to the exercises
4. 74Collecting everything that matchesUse the filter method to make a new array of just the items that match a condition.5 slides · 13 exercisesGo to the exercises
5. 75Rebuilding every itemUse the map method to make a new array of the results of converting each item.5 slides · 13 exercisesGo to the exercises

Callback functions

1. 76Remembering that a function is a valueA refresher on the feel of carrying a function around as a value. No new grammar here.3 slides · 13 exercisesGo to the exercises
2. 77Catching a function as an argumentLearn how to catch a function as an argument and call it, and build the machinery of a callback function with your own hands.5 slides · 13 exercisesGo to the exercises
3. 78Writing the function on the spotWrite a nameless function straight where the argument goes, and get the handing over done in one.4 slides · 13 exercisesGo to the exercises
4. 79Handing values to a callbackHand values over as you call the function you caught, and build the machinery by which a callback catches arguments.5 slides · 13 exercisesGo to the exercises

Loop without counting

1. 80Looping without numbersTake an array one item at a time in the form for (const fruit of fruits), with no number to keep.6 slides · 13 exercisesGo to the exercises

Pull out only what you need

1. 81Taking things out of an objectTurn just the entries you need into variables all at once, in the form const { name, age } = user;.6 slides · 13 exercisesGo to the exercises
2. 82Taking things out of an arrayTurn an array's contents into variables from the front in order, in the form const [first, second] = ranking;.5 slides · 13 exercisesGo to the exercises

Spread out, and gather up

1. 83Spreading things outBuild a new array or object, leaving the original as it was, in the form [...fruits, "peach"].6 slides · 13 exercisesGo to the exercises
2. 84Arguments that catch any numberCatch any number of arguments and handle them as an array, in the form function total(...numbers) {}.5 slides · 13 exercisesGo to the exercises

Follow a value that may be missing

1. 85Following an entry that may not be thereUse ?. so you can follow past an entry that may not be there without stopping.5 slides · 13 exercisesGo to the exercises

Map and Set

1. 86Map, which holds key and value pairsMake a new Map() and add, take and count key and value pairs.6 slides · 13 exercisesGo to the exercises
2. 87Set, a collection with no duplicatesUse new Set() to build a collection where the same value cannot go in twice.5 slides · 13 exercisesGo to the exercises

Catch an error

1. 88Not stopping at an errorWrite the work that might fail in the try, and what to do when it failed in the catch.5 slides · 13 exercisesGo to the exercises

Throw your own error

1. 89Throwing an error yourselfTurn an odd value away on the spot with throw, and catch it on the calling side.5 slides · 13 exercisesGo to the exercises