But in CSS itself not all properties are inherited.… But just as we expose methods to interact with our component, we can expose CSS variables (custom CSS… Custom CSS properties exist on all levels, both in light and shadow.… CSS custom properties pierce through shadow DOM.… They are used as “hooks” to style the component:
The component uses a custom CSS property to style key
We can create custom HTML elements, described by our class, with its own methods and properties, events… There are two kinds of custom elements:
Autonomous custom elements – “all-new” elements, extending the… Customized built-in elements – extending built-in elements, like a customized button, based on HTMLButtonElement… Custom element name must contain a hyphen -
Custom element name must have a hyphen -, e.g… That leads to important consequences for custom elements.
Property-attribute synchronization.When a standard attribute changes, the corresponding property is auto-updated… DOM properties are typed.DOM properties are not always strings.… Properties – is what’s in DOM objects.… A small comparison:
Properties
Attributes
Type
Any value, standard properties have types described… The value of the DOM property may be different, for instance the href property is always a full URL,
Such as <input type="range">:
The browser uses DOM/CSS internally to draw them.… We can use it style subelements with CSS, like this:… Shadow tree can be used in Custom Elements to hide component internals and apply component-local styles… The elem must be either a custom element, or one of: “article”, “aside”, “blockquote”, “body”, “div”,… If mode="open", then it’s accessible as elem.shadowRoot property.
Just like built-in browser <select> expects <option> items, our <custom-tabs> may expect… And a <custom-menu> may expect menu items.… The code that makes use of <custom-menu> can look like this:… That’s possible, but if we’re moving elements to shadow DOM, then CSS styles from the document do not… There are many <li slot="item"> in the <custom-menu>, but only one <slot name
CSS events:
transitionend – when a CSS-animation finishes.
There are many other events.… DOM property.We can assign a handler using a DOM property on<event>.… As there’s only one onclick property, we can’t assign more than one event handler.… There are more properties.… DOM property: elem.onclick = function.
Although, mouse events don’t have necessary properties to handle such multi-touches.… Although, we may need to add touch-action: none in some places in CSS.… We can use this property to react differently on various pointer types.… These properties aren’t supported by most devices, so they are rarely used.… Device-specific properties, such as pressure, width/height, and others.
this:
Here’s how it looks with some CSS… We can add nested lists and style them using CSS to “slide down”.… Chrome), passive is true by default for touchstart and touchmove events.
event.defaultPrevented.The property… don’t abuse
Technically, by preventing default actions and adding JavaScript we can customize… But if we make a button behave as a link using JavaScript and even look like a link using CSS, then &
CSS properties with a word cubic-bezier will have an icon before this word.… Performance.Most CSS properties can be animated, because most of them are numeric values.… However, not all animations will look as smooth as you’d like, because different CSS properties cost… You can find a longer list of CSS properties and which stages they trigger at https://csstriggers.com… The transform property is a great choice, because:
CSS transforms affect the target element box as a
Custom events can be used to create “graphical components”.… Later we’ll see what it means for custom events.… The bubbling mechanics is the same for built-in (click) and custom (hello) events.… In the second argument (object) we can add an additional property detail for any custom information that… For custom events we should use CustomEvent constructor.
But they also may have other properties of their own, e.g.… The parent constructor sets the message property.… (property).… And then inherit all our custom errors from it.
Let’s call it MyError.… Then name property can be used for such checks.
As we know, objects can store properties.… Until now, a property was a simple “key-value” pair to us.… Property flags.Object properties, besides a value, have three special attributes (so-called “flags”):… Sets configurable: false for all existing properties.… Object.isSealed(obj)
Returns true if adding/removing properties is forbidden, and all existing properties
There are two kinds of object properties.
The first kind is data properties.… All properties that we’ve been using until now were data properties.… The second type of property is something new. It’s an accessor property.… Accessor descriptors.Descriptors for accessor properties are different from those for data properties… as for data properties,
configurable – same as for data properties.
That actually does the same as assigning it as a property… such code won’t work:
Static properties… Static properties are also possible, they look like regular class properties, but prepended by static… and methods.Static properties and methods are inherited.… Static properties are used when we’d like to store class-level data, also not bound to an instance.
Forms and control elements, such as <input> have a lot of special properties and events.… They also have elements property that lists form controls inside them.… select and option.A <select> element has 3 important properties:
select.options – the collection… The elements property also works for <fieldset>.
element.form
Elements reference their form in… the form property.
DOM node classes.Different DOM nodes may have different properties.… corresponding to <input> has input-related properties and so on.… The tagName property exists only for Element nodes.… DOM nodes also have other properties depending on their class.… Most standard HTML attributes have a corresponding DOM property.
CSS styles, applied to the component.… Usually, special CSS classes and conventions are used to provide “component feel” – CSS scoping and DOM… Custom elements – to define custom HTML elements.… CSS Scoping – to declare styles that only apply inside the Shadow DOM of the component.… Event retargeting and other minor stuff to make custom components better fit the development.
Until now we were only using public properties and methods.… Now we’ll make a coffee machine in JavaScript with all these types of properties.… Let’s change waterAmount property to protected to have more control over it.… Protected properties are usually prefixed with an underscore _.… Read-only “power”.For power property, let’s make it read-only.
We should always prefer CSS classes to style.… The style property operates only on the value of the "style" attribute, without any CSS cascade… :
A computed style value is the value after all CSS rules and CSS inheritance is applied, as the result… of the CSS cascade.… getComputedStyle requires the full property name
We should always ask for the exact property
/Top.These properties are rarely needed, but still they are the “most outer” geometry properties, so… Geometry properties are zero/null for elements that are not displayed
Geometry properties… There are two reasons:
First, CSS width/height depend on another property: box-sizing that defines… “what is” CSS width and height.… The element with text has CSS width:300px.
Why derived properties are needed? Why does top/left exist if there’s x/y?… So the additional derived properties are for convenience.… Coordinates right/bottom are different from CSS position properties
There are obvious similarities… between window-relative coordinates and CSS position:fixed.… But in CSS positioning, right property means the distance from the right edge, and bottom property means
Properties and methods are described in the specification: DOM Living Standard.… CSSOM for styling
There’s also a separate specification, CSS Object Model (CSSOM) for CSS… (usually we just add/remove CSS classes, not modify their CSS rules), but that’s also possible.… There are many properties, but the two most widely known are: navigator.userAgent – about the current… It takes the DOM specification and extends it with many additional properties and methods.
We can also set a custom logic in the static method Symbol.hasInstance.… That’s how we can customize the behavior of instanceof.… That can lead to interesting consequences when a prototype property is changed after the object is created… Symbol.toStringTag.The behavior of Object toString can be customized… using a special object property Symbol.toStringTag.
querySelector.The call to elem.querySelector(css) returns the first element for the given CSS selector… The elem.matches(css) does not look for anything, it merely checks if elem matches the given CSS-selector… The method elem.closest(css) looks for the nearest ancestor that matches the CSS-selector.… Besides that:
There is elem.matches(css) to check if elem matches the given CSS selector.… There is elem.closest(css) to look for the nearest ancestor that matches the given CSS-selector.
JavaScript animations can handle things that CSS can’t.… properties.… timing(timeFraction)
Timing function, like CSS-property transition-timing-function that gets the fraction… Unlike CSS, we are not limited to Bezier curves here.… The same is true about draw: we can animate anything, not just CSS properties.
Naturally, such a string should include all important properties.… are added, old properties are renamed and removed.… in properties?… If we pass an array of properties to it, only these properties will be encoded.… But the list of properties is quite long.
When we perform actions with the object, e.g. take a property user.name, the JavaScript engine looks… The value of user is constant, it must always reference the same object, but properties of that object… We’ll mention that in the chapter Property flags and descriptors.… Nested cloning.Until now we assumed that all properties of user are primitive.… But properties can be references to other objects.
There are many ways to initiate a scroll, so it’s more reliable to use CSS, overflow property.
Their internal implementation uses the object’s constructor property for that.… Even more, we can customize that behavior.… That was thoroughly explained in the article Static properties and methods.
Connection status: readyState.The EventSource object has readyState property, that has one of three values… We can query this property to know the state of EventSource.… For example:
To handle custom events… The current state is in the readyState property.… The server may set a custom event name in event:.
This is governed by the composed event object property.… Custom events.When we dispatch custom events, we need to set both bubbles and composed properties to
For instance, CSS\d matches a string CSS with a digit after it:… Unicode encoding, used by JavaScript for strings, provides many properties for characters, like: which… We can search by these properties as well. That requires flag u, covered in the next article.
To apply alternation to a chosen part of the pattern, we can enclose it in parentheses:
I love HTML|CSS… matches I love HTML or CSS.… I love (HTML|CSS) matches I love HTML or I love CSS.
The “name” property.Function objects contain some useable properties.… Custom properties.We can also add properties of our own.… Function properties can replace closures sometimes.… Here we covered their properties:
name – the function name.… Also, functions may carry additional properties.
used style.background to change the background color of document.body, but there are many other properties… At the right part of the tools there are the following subtabs:
Styles – we can see CSS applied to the… Computed – to see CSS applied to the element by property: for each property we can see a rule that gives… it (including CSS inheritance and such).… DOM nodes have properties and methods that allow us to travel between them, modify them, move around
Bezier curves are used in computer graphics to draw shapes, for CSS animation and in many other places… but very needed insight into what Bezier curves are, while the next one shows how we can use them for CSS… A curve is always inside the convex hull of control points:
Because of that last property, in computer… Good properties of Bezier curves:
We can draw smooth lines with a mouse by moving control points.… In CSS animation to describe the path and speed of animation.
And we can use it in CSS rules too.… The pattern has two parts:
We add a custom attribute to an element that describes its behavior.
It’s forbidden to generate “custom” clipboard events with dispatchEvent in all browsers except Firefox… The event.clipboardData property gives access to the clipboard.
That wrapper returns a promise and forwards the call to the original f, tracking the result in the custom… Then our custom callback is in exactly the right format, and promisify works great for such a case.
Methods and properties are:
new Map() – creates the map.
map.set(key, value) – stores the value by the… This algorithm can’t be changed or customized.… Methods and properties:
new Map([iterable]) – creates the map, with optional iterable (e.g. array) of… Additional convenient methods, the size property.
Set – is a collection of unique values.… Methods and properties:
new Set([iterable]) – creates the set, with optional iterable (e.g. array) of
In the browser, we can make a variable window-level global by explicitly assigning it to a window property… As you can see, when 1.js changes the name property… On the first import we initialize it, write to its properties.… Here, admin.js exports the config object (initially empty, but may have default properties… “Special” module types like HTML/CSS modules are also supported.
Once the server has responded, we can receive the result in the following xhr properties… We can also specify a timeout using the corresponding property:… Response Type.We can use xhr.responseType property… note:
In the old scripts you may also find xhr.responseText and even xhr.responseXML properties… HTTP-headers.XMLHttpRequest allows both to send custom headers and read headers from the response.
There are other non-standard properties available in most environments.… Throwing our own errors.What if json is syntactically correct, but doesn’t have a required name property… And in the browser we can assign a function to the special window.onerror property, that will run in… That JS script sets a custom window.onerror function.… Error objects have following properties:
message – the human-readable error message.
name – the string
JavaScript doesn’t allow you to customize how operators work on objects.… In this chapter we’ll cover how an object converts to primitive and how to customize it.… Let’s implement these methods to customize the conversion.
One of them is to use custom events, we’ll cover them later.… In fact, the capturing phase was invisible for us, because handlers added using on<event>-property… There’s a property event.eventPhase that tells us the number of the phase on which the event was caught… Each handler can access event object properties:
event.target – the deepest element that originated
The reason for this is that the script may want to get coordinates and other style-dependent properties… This event is available via the onload property.… So right now old browsers still may show it as a message, but aside of that – there’s no way to customize… The document.readyState property tells us about the current loading state.
Now let’s add a custom constructor to Rabbit.… A derived constructor has a special internal property [[ConstructorKind]]:"derived".… [[HomeObject]].To provide the solution, JavaScript adds one more special internal property for functions… When a function is specified as a class or object method, its [[HomeObject]] property becomes that object… Internals:
Methods remember their class/object in the internal [[HomeObject]] property.
A property is a “key: value” pair, where key is a string (also called a “property name”), and value can… In the user object, there are two properties:
The first property has the name "name" and the… That’s called computed properties.… Property value shorthand.In real code, we often use existing variables as values for property names.… The use-case of making a property from a variable is so common, that there’s a special property value
Such properties are called “inherited”.… The __proto__ property is a bit outdated.… So writing to such a property is actually the same as calling a function.… And for..in only lists enumerable properties.… Properties from the prototype are not taken into account.
Summary.
The only thing that worked reliably was a "prototype" property of the constructor function,… Please note that F.prototype here means a regular property named "prototype" on F.… It sounds something similar to the term “prototype”, but here we really mean a regular property with… If, after the creation, F.prototype property changes (F.prototype = <another object>), then new… Default F.prototype, constructor property.Every function has the "prototype" property even
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