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Objects allow us to create a single entity that stores data items by key.… Arrays allow us to gather data items into an ordered list.… The rest ‘…’.Usually, if the array is longer than the list at the left, the “extra” items are omitted… In the simplest case, that’s a list of variable names in {...}.… It may have a width, a height, a title, an item list and so on.

The == operator doesn’t do item-by-item comparison.… Instead, compare them item-by-item in a loop or using iteration methods explained in the next chapter… We can use an array as a deque with the following operations: push(...items) adds items to the end.… ) adds items to the beginning.… Instead you can use for..of loop to compare arrays item-by-item.

And a <custom-menu> may expect menu items.… ="item"> in the template.… So all such <li slot="item"> are appended to <slot name="item"> one after… another, thus forming the list.… After 1 second: slotchange: item triggers, when a new <li slot="item"> is added.

(...items) – adds items to the end, arr.pop() – extracts an item from the end, arr.shift() – extracts… an item from the beginning, arr.unshift(...items) – adds items to the beginning.… the index where it was found, otherwise -1. arr.includes(item, from) – looks for item starting from… We have a set of some items.… ..items) – adds items to the beginning. splice(pos, deleteCount, ...items) – at index pos deletes deleteCount

Arguments of these methods are an arbitrary list of DOM nodes to insert, or text strings (that become… Here’s an example of using these methods to add items to a list and the text before/after it:… Here’s a visual picture of what the methods do: So the final list… For example, getListContent below generates a fragment with <li> items, that are later inserted… The following code inserts a new list item before the second <li>:

Also the method .on(name, handler) that adds handler function as the listener to events with the given… …And the method .off(name, handler) that removes the handler listener.… Or, a menu can generate the event "select" when a menu item is selected, and other objects… . .off(eventName, handler) – removes the function from the handlers list. .trigger(eventName, ...args… ) – generates the event: all handlers from _eventHandlers[eventName] are called, with a list of arguments

Spread syntax.We’ve just seen how to get an array from the list of parameters.… Passing it “as is” won’t work, because Math.max expects a list of numeric arguments, not a single array… items in the code Math.max(arr[0], arr[1], arr[2]), because we may be unsure how many there are.… The list of characters is passed to array initializer [...str].… Together they help to travel between a list and an array of parameters with ease.

Linked list.Imagine, we want to store an ordered list of objects.… next linked list element or null if that’s the end.… Naturally, lists are not always better than arrays. Otherwise everyone would use only lists.… But in the list we need to start from the first item and go next N times to get the Nth element.… a list (or null).

The property list is applied to the whole object structure.… So the objects in participants are empty, because name is not in the list.… Let’s include in the list every property except room.occupiedBy that would cause the circular reference… But the list of properties is quite long.… Please note that replacer function gets every key/value pair including nested objects and array items

JS-based menu may trigger events telling what happens with the menu: open (menu open), select (an item… Another code may listen for the events and observe what’s happening with the menu.… MouseEvent, KeyboardEvent and others.Here’s a short list of classes for UI Events from the UI Event specification… The full list of properties for different UI events is in the specification, for instance, MouseEvent… Any handler can listen for that event with rabbit.addEventListener('hide',...) and, if needed, cancel

If an object isn’t technically an array, but represents a collection (list, set) of something, then for… the object, examines it for being an iterable or array-like, then makes a new array and copies all items… The optional arguments mapFn and thisArg allow us to apply a function to each item.

) – delete everything. key(index) – get the key on a given position. length – the number of stored items… If both windows are listening for window.onstorage, then each one will react on updates that happened… clear() – delete everything. key(index) – get the key number index. length – the number of stored items

The list varies a bit between browsers, but one thing is always correct: focus/blur support is guaranteed… For instance, here’s a list.… Click the first item and press Tab:

show up: The Sources panel has 3 parts: The File Navigator pane lists… Now you could click the same toggler again to hide the resources list and give the code some space.… We can always find a list of breakpoints in the right panel.… If you click on a stack item (e.g.

It runs the func setting this=context and using an array-like object args as the list… The only syntax difference between call and apply is that call expects a list of arguments, while apply… only a subtle difference regarding args: The spread syntax ... allows to pass iterable args as the list… …Do so until this.length items are glued. Return result.… arguments. func.apply(context, args) – calls func passing context as this and array-like args into a list

They are listed in the Proxy specification and in the table below.… The full invariants list is in the specification.… …But all of them start with that list.… Other traps exist: the full list is in the beginning of this article.… For instance, Map stores items in the internal slot [[MapData]].

The call returns openRequest object, we should listen to events on it: success: database is ready, there… We should listen for it and close the old database connection (and probably suggest a page reload, to… Or we can just examine the database: get a list of existing object stores as db.objectStoreNames.… Add the item to their inventory.… For each value of that field, it stores a list of keys for objects that have that value.

Some methods in prototypes may overlap, for instance, Array.prototype has its own toString that lists… The object itself stores only the data (array items, object properties, the date) Primitives also store

Event Listeners – to see event listeners attached to DOM elements (we’ll cover them in the next part… For instance, $0.style.background = 'red' makes the selected list item red, like this:

umbrella” term to represent one of views over ArrayBuffer: Int8Array, Uint8Array and so on, the full list… Its byte length will be length multiplied by the number of bytes in a single item TypedArray.BYTES_PER_ELEMENT… one view to another: Here’s the list

way to do many things, from copying and moving documents (as in file managers) to ordering (dropping items… So we should listen on document to catch it.

Here’s how it looks with some CSS: Menu items… We can add nested lists and style them using CSS to “slide down”.

To iterate over such an object, we should use a for await (let item of iterable) loop.… For instance, when we need a list of users, a request returns a pre-defined count (e.g. 100 users) –

Like this: list → lst. userAgent → ua. browser → brsr.… Like obj, data, value, item, elem and so on. The ideal name for a variable is data.

That has two effects: It allows to get a part of the match as a separate item in the result array.… , the corresponding result array item is present and equals undefined.… instance, if we want to find (go)+, but don’t want the parentheses contents (go) as a separate array item… That’s used when we need to apply a quantifier to the whole group, but don’t want it as a separate item

It has a single method abort(), And a single property signal that allows to set event listeners on it… We could implement the same kind of event listening in our code on our own, without the AbortController… It will listen to abort events on signal.… We just need to listen to its abort event in our tasks:… The “call abort()” → “listen to abort event” interaction is simple and universal.

Unicode supports many different properties, their full list would require a lot of space, so here are… the references: List all properties by a character: https://unicode.org/cldr/utility/character.jsp.… List all characters by a property: https://unicode.org/cldr/utility/list-unicodeset.jsp.… system), that may have a value: Cyrillic, Greek, Arabic, Han (Chinese) and so on, here’s the full list

It contains a comma-separated list of unsafe header names that should be made accessible.… Access-Control-Request-Headers header provides a comma-separated list of its unsafe HTTP-headers.… Access-Control-Allow-Headers must have a list of allowed headers.… Access-Control-Request-Headers – a comma-separated list of “unsafe” headers.… Access-Control-Request-Headers lists unsafe requested headers.

For instance: arr.forEach(func) – func is executed by forEach for every array item. setTimeout(func)

Also, note that the new top menu item named “Develop” has appeared.

You give your fans a list.… In terms of our analogy: this is the “subscription list”.… analogy isn’t terribly accurate, because JavaScript promises are more complex than a simple subscription list… If the singer has already released their song and then a person signs up on the subscription list, they… Each time, we’re adding a new “fan”, a new subscribing function, to the “subscription list”.

We can’t prevent scrolling by using event.preventDefault() in onscroll listener, because it triggers

operator provides a way to choose a defined value from a list of variables. The result of a ??… Functions may have local variables: those declared inside its body or its parameter list… More to come.That was a brief list of JavaScript features. As of now we’ve studied only basics.

Listen to xhr events for response.… You can find readystatechange listeners… The full list is in the specification.… There are actually more events, the modern specification lists… If we need to track uploading specifically, then we should listen to same events on xhr.upload object

Once the socket is created, we should listen to events on it.… The header Sec-WebSocket-Extensions is sent automatically by the browser, with the list of all extensions… The server should respond with a list… The full list can be found in RFC6455, §7.4.1.… For each accepted websocket, add it to the set clients.add(socket) and set message event listener to

Here’s a sketch with the full list:… We can observe attributes by providing their list in observedAttributes() static getter.… For a change of an attribute, listed in observedAttributes(), attributeChangedCallback triggers.… For instance, inner elements can dispatch events like initialized, and outer ones can listen and react

Import *.Usually, we put a list of what to import in curly braces import {...}, like this:… sight, “import everything” seems such a cool thing, short to write, why should we ever explicitly list… Explicitly listing what to import gives shorter names: sayHi() instead of say.sayHi().… Explicit list of imports gives better overview of the code structure: what is used and where.

on <p>, then the sequence is: HTML → BODY → FORM → DIV -> P (capturing phase, the first listener… ): P → DIV → FORM → BODY → HTML (bubbling phase, the second listener).… Please note, the P shows up twice, because we’ve set two listeners: capturing and bubbling.… Listeners on the same element and same phase run in their set order If we have multiple event

to select the first value from a list that isn’t null/undefined.… provides a short way to choose the first “defined” value from a list.

An object can be created with figure brackets {…} with an optional list of properties.… The last property in the list… The object may be used to suggest a list… …On the other hand, if the keys are non-integer, then they are listed

…But why does hasOwnProperty not appear in the for..in loop like eats and jumps do, if for..in lists… And for..in only lists enumerable properties.… That’s why it and the rest of the Object.prototype properties are not listed.

The childNodes collection lists all child nodes, including text nodes.… collections are read-only DOM collections, and even more – all navigation properties listed… Element-only navigation.Navigation properties listed

But often we need to create many similar objects, like multiple users or menu items and so on.

writable – if true, the value can be changed, otherwise it’s read-only. enumerable – if true, then listed… in loops, otherwise not listed. configurable – if true, the property can be deleted and these attributes

Here’s a list of the most useful DOM events, just to take a look at: Mouse events: click – when the… handler function. options An additional optional object with properties: once: if true, then the listener… Please note that we need to explicitly setup the events to listen using addEventListener.

Then use new MyClass() to create a new object with all the listed… That’s especially useful in browser environment, for event listeners.

We can set a listener on keydown and check which key is pressed.… There’s a dilemma here: in such a listener, should we check the value of event.key or event.code?… You can find the list in the specification.

Don’t try to remember the list – soon we’ll deal with each of them, and you’ll know them by heart automatically

The new promise resolves when all listed promises are resolved, and the array of their results becomes… promise rejects, Promise.all immediately rejects, completely forgetting about the other ones in the list

Let’s not argue.The editors in the lists above are those that either I or my friends whom I consider