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(text, comment, etc.) it has a string with the node type.… Other node types, such as text nodes, have their counterpart: nodeValue and data properties.… is returned, as if all <tags> were cut out, but the text in them remained.… It has a numeric value: 1 for elements,3 for text nodes, and a few others for other node types.… Instead it gets replaced with the new HTML in the outer context. nodeValue/data The content of a non-element

Every value in JavaScript has a type. What type is a function?… If the function does not provide one, then in an assignment it is figured out from the context.… There’s no local sayHi, so the outer variable is used.… And at the moment of the call that outer sayHi is null.… The outer code still has its variable sayHi or welcome.

The text inside a tag is an object as well.… The text inside elements forms text nodes, labelled as #text. A text node contains only a string.… Other node types.There are some other node types besides elements and text nodes.… There are 12 node types.… Text nodes are shown just as text. And there are no “blank” (space only) text nodes at all.

Pressing a mouse button over a text and moving it – selects the text.… menu we’d like to implement document-wide context menu.… We forever deny access to information about right-clicks for any outer code, including counters that… If we have nested elements, and each of them has a context menu of its own, that would also work.… Nested context menus architecture There are also alternative ways to implement nested context

Name a variable by its type: str, num… Give them a try.… The value type is easy to find out by debugging. But what’s the meaning of the variable?… There’s just no way to figure out without a good meditation!… And the function printText(text) will put the text on-screen.… Overlap outer variables.When in the light, can’t see anything in the darkness.

Technically, if we have a text field to hack, then we can position an iframe in such a way that text… Everything that the visitor types will be hidden, because the iframe is not visible.… People will usually stop typing when they can’t see their new characters printing on the screen.… this: That is: if the window finds out… That <div> is to be removed if window == top or if we figure out that we don’t need the protection

case of such operations, objects are auto-converted to primitives, and then the operation is carried out… Conversion rules.In the chapter Type Conversions we’ve seen the rules for numeric, string and boolean… All objects are true in a boolean context, as simple as that.… There are three variants of type conversion, that happen in various situations.… "default" Occurs in rare cases when the operator is “not sure” what type to expect.

Safe requests.There are two types of cross-origin requests: Safe requests. All the others.… with the value application/x-www-form-urlencoded, multipart/form-data or text/plain.… is not one of: application/x-www-form-urlencoded, multipart/form-data, text/plain.… ,API-Key are in the list Access-Control-Allow-Headers, so it sends out the main request.… /x-www-form-urlencoded, multipart/form-data or text/plain.

We can type commands there and press Enter to execute.… Global has global variables (out of any functions).… – “Step out”: continue the execution till the end of the current function, hotkey Shift+F11.… Continue to here Right click on a line of code opens the context menu with a great option… Don’t forget about the right click and context menus!

Send it out.… xhr.responseType property to set the response format: "" (default) – get as string, "text… quot; – get as XML document (can use XPath and other XML methods) or HTML document (based on the MIME type… Just don’t forget to set the header Content-Type: application/json, many server-side frameworks automatically… upload aborted. error – non-HTTP error. load – upload finished successfully. timeout – upload timed out

Most of the time, operators and functions automatically convert the values given to them to the right type… There are also cases when we need to explicitly convert a value to the expected type.… Explicit conversion is usually required when we read a value from a string-based source like a text… Summary.The three most widely used type conversions are to string, to number, and to boolean.

There is no separate type for a single character.… are other, less common special characters: Character Description \n New line \r In Windows text… The same algorithm can be layed out… Letters with diacritical marks are “out… There are 3 types of quotes.

There are eight basic data types in JavaScript.… We can put any type in a variable.… In JavaScript, there is no such type. There’s only one type: string.… Boolean (logical type).The boolean type has only two values: true and false.… Functions belong to the object type.

Reference type explained.Looking closely, we may notice two operations in obj.method() statement: First… The Reference Type is a “specification type”.… The result of a property access user.hi is not a function, but a value of Reference Type.… Reference type is a special “intermediary” internal type, with the purpose to pass information from dot… Summary.Reference Type is an internal type of the language.

By specification, only two primitive types may serve as object property keys: string type, or symbol… type.… Otherwise, if one uses another type, such as number, it’s autoconverted to string.… A value of this type can be created using Symbol():… Summary.Symbol is a primitive type for unique identifiers.

When you move the mouse, you can see mouse events in the text area.… We don’t really want to process in and out of each one.… There are mouseover/out handlers on #parent element that output event details.… Let’s filter them out.… Events mouseover/out and mouseenter/leave have an additional property: relatedTarget.

This is that function that actually draws out the animation.… Here’s the animated “bouncing” text typing: Resultstyle.cssindex.htmlSummary.For animations that CSS

variable: The diagram below depicts two types… Then, at some point, we stop using the user variable – it gets overwritten, goes out… One way to handle this problem – is to periodically scavenge the cache and clear out… If the object that creates the FinalizationRegistry instance goes out of scope or is deleted, the cleanup… In the context of JavaScript, the “main” program – is our JavaScript-code, that runs and executes in

text text text text text text text text text text text text text text text text text text text text… text text text text text text text text text text text text text text text text text text text text text… text text text text text text text text text text text text text text text text text text text text… text text text text text text text text text text text text text text text text text text text text text… text text text text text text text text text text text text text text text text text text text text text

For text inputs that means that the event occurs when it loses focus.… For instance, while we are typing in the text field below – there’s no event.… So the example above uses document.getSelection() to get the selected text.… It’s possible to copy/paste not just text, but everything.… For text inputs triggers on focus loss. input For text inputs on every change.

For example, we need to show a nice-looking message when a visitor logs in, logs out and maybe somewhere… If a same-named variable is declared inside the function then it shadows the outer one.… As the value for text isn’t passed, it becomes undefined.… parameter is not passed, it will get the value "no text given".… A function may access outer variables. But it works only from inside out.

methods to access the body in various formats: response.text() – read the response and return as text… header is set to text/plain;charset=UTF-8 by default.… header manually, because a Blob object has a built-in type (here image/png, as generated by toBlob).… For Blob objects that type becomes the value of Content-Type.… Methods to get response body: response.text() – return the response as text, response.json() – parse

Event: submit.There are two main ways to submit a form: The first – to click <input type="submit… "> or <input type="image">.… In the form below: Go into the text field and press Enter.… Click <input type="submit">.… When a form is sent using Enter on an input field, a click event triggers on the <input type

commonly referred to as “lookaround”) are useful when we’d like to match something depending on the context… That is: match everything, in any context, and then filter by context in the loop.… str.matchAll (always) return matches as arrays with index property, so we know where exactly in the text… it is, and can check the context.… Lookaround types: Pattern type matches X(?=Y) Positive lookahead X if followed by Y X(?!

: It shows a modal window with a text… title The text to show the visitor. default An optional second parameter, the initial value for the input… The visitor can type something in the prompt input field and press OK.… Then we get that text in the result.… The call to prompt returns the text from the input field or null if the input was canceled.

for building a polymorphic function, the one that treats arguments differently depending on their type… By specification, the built-in toString can be extracted from the object and executed in the context… in the chapter Decorators and forwarding, call/apply to execute the function objectToString in the context… At the end we have “typeof on steroids” that not only works for primitive data types, but also for built-in… We can use {}.toString.call instead of instanceof for built-in objects when we want to get the type as

But when we sort things out, everything becomes fairly simple.… on argument types.… there’s no single-value type like int, or int8 in JavaScript.… Out-of-bounds behavior.What if we attempt to write an out-of-bounds value into a typed array?… For typed arrays, the constructor dictates what the format is.

And in such functions we usually don’t want to leave the current context.… Here in forEach, the arrow function is used, so this.title in it is exactly the same as in the outer… The lookup of this is made exactly the same way as a regular variable search: in the outer lexical environment… Class inheritance That’s because they are meant for short pieces of code that do not have their own “context

The value of this is evaluated during the run-time, depending on the context… If there’s this inside a function, it expects to be called in an object context.… If we reference this from such a function, it’s taken from the outer “normal” function.… , it’s useful when we actually do not want to have a separate this, but rather to take it from the outer… context.

both client and server can exchange messages One-directional: only server sends data Binary and text… data Only text WebSocket protocol Regular HTTP EventSource is a less-powerful way of communicating… The server should respond with status 200 and the header Content-Type: text/event-stream, then keep the… special format, like this: A message text… The server may specify another type of event with event: ... at the event start.

After it ends, the old execution context is retrieved from the stack, and the outer function is resumed… in the execution context stack.… context is on top (and bold), and previous remembered contexts are below.… A new execution context is created, the previous one is pushed on top of the stack: Context:… Contexts take memory.

Variables are dynamically typed.… with a single value null, meaning “empty” or “does not exist”, undefined – a type with a single value… More in: Variables and Data types.… converts the operand to boolean type and returns the inverse value.… Later we’ll study more types of loops to deal with objects.

How to make sure that it will be called in the right context?… For instance, we have a function send(from, to, text).… Going partial without context.What if we’d like to fix some arguments, but not the context this?… We can’t just omit the context and jump to arguments.… context this and first arguments if given.

Second, more often we get a file from <input type="file"> or drag’n’drop or other browser… That’s how we can get a File object from <input type="file">:… blob) – read the data in binary format ArrayBuffer. readAsText(blob, [encoding]) – read the data as a text… slicing, File inherits from Blob, so we can call them directly, without reading. readAsText – for text

For instance, here <body> has children <div> and <ul> (and few blank text nodes):… The childNodes collection lists all child nodes, including text nodes.… For instance, in childNodes we can see both text nodes, element nodes, and even comment nodes if they… But for many tasks we don’t want text or comment nodes.… Certain types of DOM elements may provide additional properties, specific to their type, for convenience

array of attribute names, to observe only selected ones. characterData – whether to observe node.data (text… MutationRecord objects have properties: type – mutation type, one of "attributes": attribute… modified "characterData": data modified, used for text nodes, "childList": child… namespace (for XML) of the changed attribute, oldValue – the previous value, only for attribute or text… If we run this code in the browser, then focus on the given <div> and change the text inside <

It’s encoded and sent out with Content-Type: multipart/form-data.… given name and value, formData.append(name, blob, fileName) – add a field as if it were <input type… Sending a form with a file.The form is always sent as Content-Type… So, <input type="file"> fields are sent also, similar to a usual form submission.… needed, the last argument is a file name, that normally is taken from user filesystem for <input type

gt; tag has a few attributes that are rarely used nowadays but can still be found in old code: The type… attribute: <script type=…> The old HTML standard, HTML4, required a script to have a type.… Usually it was type="text/javascript". It’s not required anymore.… The type and language attributes are not required.

There are two main types of code editors: IDEs and lightweight editors.… Many people use one tool of each type.… There are many options, for instance: Sublime Text (cross-platform, shareware).

The browser considers <template> content “out… template.The template content is available in its content property as a DocumentFragment – a special type… <template> content is considered “out of the document”, so it doesn’t affect anything.

As an example, in the code below we call sayHi in the context of different objects: sayHi.call(user)… Passing all arguments along with the context to another function is called call forwarding.… The main job is still carried out by the function.… To implement cachingDecorator, we studied methods: func.call(context, arg1, arg2…) – calls func with… given context and arguments. func.apply(context, args) – calls func passing context as this and array-like

If you came to this article searching for other types of loops, here are the pointers: See for…in to… Labels for break/continue.Sometimes we need to break out from multiple nested loops at once.… looks upwards for the label named outer and breaks out of that loop.… Summary.We covered 3 types of loops: while – The condition is checked before each iteration. do..while… A label is the only way for break/continue to escape a nested loop to go to an outer one.

Such as <input type="range">: The browser uses DOM/CSS internally to draw them.… Then <input type="range"> looks like this: What you see under #shadow-root… Shadow tree.A DOM element can have two types of DOM subtrees: Light tree – a regular DOM subtree, made… Browser-native shadow trees, such as <input type="range">, are closed.… Style rules from the outer DOM don’t get applied.

mouseup Mouse button is clicked/released over an element. mouseover/mouseout Mouse pointer comes over/out… There are other ways to open a context menu, e.g. using a special keyboard key, it triggers in that case… Please note: the text inside it is still selectable.… However, the selection should start not on the text itself, but before or after it.… The default browser action of mousedown is text selection, if it’s not good for the interface, then it

object with two properties: done – true when the reading is complete, otherwise false. value – a typed… Prior to reading, we can figure out the full response length from the Content-Length header.… those, so there’s some code to do that: We create chunksAll = new Uint8Array(receivedLength) – a same-typed

frames” – contain text data that parties send to each other.… In the browser, we directly work only with text or binary frames.… WebSocket .send() method can send either text or binary data.… No settings are required: just send it out in any format.… When we receive the data, text always comes as string.

But what happens if outer variables change since a function is created?… No matter where, it still has access to the same outer variables.… A reference to the outer lexical environment, the one associated with the outer code.… The inner Lexical Environment has a reference to the outer one.… one, then the more outer one and so on until the global one.

E.g. if we have <outer><inner></inner></outer>, then <outer> element is… So the outer element finishes the initialization before the inner one.… connected. inner connected. outer initialized. inner initialized.… We can clearly see that the outer element finishes initialization (3) before the inner one (4).… Summary.Custom elements can be of two types: “Autonomous” – new tags, extending HTMLElement.

objects like this: Arguments: type… – event type, a string like "click" or our own like "my-event".… The right constructor allows to specify standard properties for that type of event.… Browser-generated events always have the right type.… of native events like MouseEvent, KeyboardEvent and so on accept properties specific to that event type

Here are two scripts on the same page, both type="module".… Then all scripts will see it, both with type="module" and without it.… Compatibility, “nomodule”.Old browsers do not understand type="module".… Scripts of an unknown type are just ignored.… “Special” module types like HTML/CSS modules are also supported.