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As the content is “zeroed-out” and rewritten from the scratch, all images and other resources will be… " re-creates the HTML content and reloads smile.gif (hope it’s cached).… In the outer document (the DOM) we can see the new content instead of the <div>.… An example of reading the content of a text node and a comment:… Read-only. innerHTML The HTML content of the element.

Many types of components, such as tabs, menus, image galleries, and so on, need the content to render… the actual tab content to be passed.… Please note: there’s no slotchange event after 2 seconds, when the content of slot="title"… We modify the content inside the slotted element, that’s another thing.… The content of <slot> element is used as a fallback.

The initial idea was to show another content without closing the main window.… As of now, there are other ways to do that: we can load content dynamically with fetch and show it in… And here we modify the contents after loading:… Same origin policy Windows may freely access content of each other only if they come from… If you run the code below, it replaces the opener (current) window content with “Test”:

Some browsers (not all) reserve the space for it by taking it from the content (labeled as “content width… So, without scrollbar the content width would be 300px, but if the scrollbar is 16px wide (the width… That makes the element content scroll 10px down.… the space from the content in some browsers.… So the real width available for the content is less than CSS width.

access an existing selection, select/deselect DOM nodes as a whole or partially, remove the selected content… We need to create a range, that: starts from position 2 in <p> first child (taking all but two… using these methods: deleteContents() – remove range content from the document extractContents() –… remove range content from the document and return as DocumentFragment cloneContents() – clone range content… So we disable the selection to avoid conflict, still allowing elem contents to be copied.

That is actually the art of programming – to take a complex task and code it in a way that is both correct… Indents.There are two types of indents: Horizontal indents: 2 or 4 spaces.… A horizontal indentation is made using either 2 or 4 spaces or the horizontal tab symbol (key Tab).… One advantage of spaces over tabs is that spaces allow more flexible configurations of indents than the… tab symbol.

So we definitely should take a look at it.… Although, on certain strings it takes a lot of time.… Here’s what the regexp engine does: First, the regexp engine tries to find the content of the parentheses… The contents of parentheses with ?=... isn’t memorized by the engine, so wrap \w+ into parentheses.… Then the engine will memorize their contents …And allow us to reference it in the pattern as \1.

For instance, download several URLs in parallel and process the content once they are all done.… The syntax is: Promise.all takes an… For instance, the Promise.all below settles after 3 seconds, and then its result is an array [1, 2, 3… For example, the loadCached function below fetches a URL and remembers (caches) its content.… For future calls with the same URL it immediately gets the previous content from cache, but uses Promise.resolve

An element receives the focus when the user either clicks on it or uses the Tab key on the keyboard.… That’s when a user clicks somewhere else or presses Tab to go to the next form field, or there are other… quot;, then pressing Tab while in the first element – moves the focus into the second one.… The Tab key ignores such elements, but method elem.focus() works. For instance, here’s a list.… The order is like this: 1 - 2 - 0.

background color of document.body, but there are many other properties, such as: innerHTML – HTML contents… then that is automatically moved inside the body, at the end, as the HTML spec requires that all content… Here are few tips to travel between the Elements tab and the console.… For the start: Select the first <li> in the Elements tab.… Press Esc – it will open console right below the Elements tab.

And then the same visitor opens our site in another tab.… to version 2 in its upgradeneeded handler.… And it can’t be both version 1 and 2.… the first tab.… from 2 to 3, from 3 to 4 etc.

For instance, in-browser JavaScript is able to: Add new HTML to the page, change the existing content… Different tabs/windows generally do not know about each other.… A page from http://anysite.com which a user has opened must not be able to access another browser tab… It is recommended to take a look at them, at least briefly, after mastering JavaScript.

state event.button Left button (primary) 0 Middle button (auxiliary) 1 Right button (secondary) 2… (forward) 4 Most mouse devices only have the left and right buttons, so possible values are 0 or 2.… non-standard way of getting a button, with possible values: event.which == 1 – left button, event.which == 2… Preventing copying If we want to disable selection to protect our page content from copy-pasting… Surely the user has access to HTML-source of the page, and can take the content from there, but not everyone

We can use the contents of capturing groups (...) not only in the result or in the replacement string… The regular expression engine finds the first quote (['"]) and memorizes its content.… Similar to that, \2 would mean the contents of the second group, \3 – the 3rd group, and so on.

At index 1: the contents of the first parentheses.… At index 2: the contents of the second parentheses.… Let’s wrap the inner content into parentheses, like this: <(.*?)>.… Here it encloses the whole tag content.… But in practice we usually need contents of capturing groups in the result.

If there’s a property styled both in :host locally, and in the document, then the document style takes… important, for such properties, local styles take precedence.… Local styles do not affect slotted content.… Smith</p> becomes bold, because CSS inheritance is in effect between the <slot> and its contents… Document styles can affect: shadow host (as it lives in the outer document) slotted elements and their contents

There may be 2, 3, 4 or more.… 2 → 3, 3 → 4.… There will be N-2 segments. Repeat step 2 until there is only one point.… Usually we take 2-3 points, and for complex lines glue several curves together.… 0 + 2(1−t)t * 0.5 + t2 * 1 = (1-t)t + t2 = t y = (1−t)2 * 0 + 2(1−t)t * 1 + t2 * 0 = 2(1-t)t = –2t2 +

Let’s see how it works. localStorage demo.The main features of localStorage are: Shared between all tabs… Another tab with the same page will have a different storage.… But it is shared between iframes in the same tab (assuming they come from the same origin).… The data survives page refresh, but not closing/opening the tab. Let’s see that in action.… That’s exactly because sessionStorage is bound not only to the origin, but also to the browser tab.

For many years a script from one site could not access the content of another site.… But as it’s forbidden to access the content of an <iframe> from another site, it wasn’t possible… , Content-Type with the value application/x-www-form-urlencoded, multipart/form-data or text/plain.… Content-Length Content-Type Expires Last-Modified Pragma Accessing any other response header causes… Headers – we can set only: Accept Accept-Language Content-Language Content-Type to the value application

as URL.A Blob can be easily used as a URL for <a>, <img> or other tags, to show its contents… Thanks to type, we can also download/upload Blob objects, and the type naturally becomes Content-Type… By clicking on a link you download a dynamically-generated Blob with hello world contents as a file:… URL.createObjectURL takes… From Blob to stream.When we read and write to a blob of more than 2

part of the string before the match $' inserts a part of the string after the match $n if n is a 1-2… digit number, inserts the contents of n-th capturing group, for details see Capturing groups $<name… > inserts the contents of the parentheses with the given name, for details see Capturing groups… arguments func(match, p1, p2, ..., pn, offset, input, groups): match – the match, p1, p2, ..., pn – contents… parentheses, so the replacement function is called with 5 arguments: the first is the full match, then 2

other words, they return the width/height of the visible part of the document, available for the content… document.Theoretically, as the root document element is document.documentElement, and it encloses all the content… If it occupied some space, then that space is now free and the content “jumps” to fill it.… the scrollbar disappeared), then add padding to document.body in place of the scrollbar to keep the content… Summary.Geometry: Width/height of the visible part of the document (content area width/height): document.documentElement.clientWidth

attribute names, to observe only selected ones. characterData – whether to observe node.data (text content… highlighting for above snippet in Prism, Prism.highlightElem(pre) is called, which examines the contents… Do we need to put the highlighting call everywhere, to highlight the code in content after loading?… And what if the content is loaded by a third-party module?… For example, we have a forum written by someone else, that loads content dynamically, and we’d like to

The following example will show the message every 2 seconds.… The actual interval between alerts will be shorter than 2 seconds.… It is possible that func’s execution turns out to be longer than we expected and takes more than 100ms… They may take much more memory than the function itself.… The browser tab is in the background mode. The laptop is on battery saving mode.

The server should respond with status 200 and the header Content-Type: text/event-stream, then keep the… Also, there will be no reconnection if the response has an incorrect Content-Type… Full example.Here’s the server that sends messages with 1, 2,… connection state: either EventSource.CONNECTING (=0), EventSource.OPEN (=1) or EventSource.CLOSED (=2)

\s (“s” is from “space”) A space symbol: includes spaces, tabs \t, newlines \n and few other rare characters… But if a regexp doesn’t take spaces into account, it may fail to work.… \s – space symbols, tabs, newlines. \S – all but \s. \w – Latin letters, digits, underscore '_'.

Here we have only one file, so we just take input.files[0].… It delivers the data using events, as reading from disk may take time.… In many cases though, we don’t have to read the file contents.

It takes exactly that much space in the memory.… Uint16Array – treats every 2 bytes as an integer, with possible values from 0 to 65535.… binary data in an ArrayBuffer of 16 bytes can be interpreted as 16 “tiny numbers”, or 8 bigger numbers (2… bytes each), or 4 even bigger (4 bytes each), or 2 floating-point values with high precision (8 bytes… Array, or any array-like object is given, it creates a typed array of the same length and copies the content

When we perform actions with the object, e.g. take a property user.name, the JavaScript engine looks… We can use either variable to access the object and modify its contents:… we later use another key (user), we are still opening the same cabinet and can access the changed contents… may need to use a combination of cloning methods, write custom code or, to not reinvent the wheel, take

So if a cookie has sensitive content that should never be sent over unencrypted HTTP, the secure flag… To understand how it works and when it’s useful, let’s take a look at XSRF attacks.… Such a protection takes time to implement though.… Then the website can set them and let people see the content.… No one likes to see such “must-click” modal splash screens instead of the content.

Surrogate pairs.All frequently used characters have 2-byte codes (4 hex digits).… Initially, JavaScript was based on UTF-16 encoding that only allowed 2 bytes per character.… But 2 bytes only allow 65536 combinations and that’s not enough for every possible symbol of Unicode.… So rare symbols that require more than 2 bytes are encoded with a pair of 2-byte characters called “a… As a side effect, the length of such symbols is 2:

part of the string before the match $' inserts a part of the string after the match $n if n is a 1-2… digit number, then it inserts the contents of n-th parentheses, more about it in the chapter Capturing… groups $<name> inserts the contents of the parentheses with the given name, more about it in

So when worker.slow(2) is executed, the wrapper gets 2 as an argument and this=worker (it’s the object… The native Map takes single value only as the key.… Append glue and this[2]. …Do so until this.length items are glued. Return result.… So, technically it takes this and joins this[0], this[1] …etc together.… It is quite common to take array methods and apply them to arguments.

Here’s a list of the most useful DOM events, just to take a look at: Mouse events: click – when the… assigned using an HTML-attribute then the browser reads it, creates a new function from the attribute content… In the code below button shows its contents using this.innerHTML:… So the last line actually takes the result of the function execution, that is undefined (as the function… When the browser reads the attribute, it creates a handler function with body from the attribute content

For example, to calculate pow(2, 4) the recursive variant does these steps: pow(2, 4) = 2 * pow(2, 3… ) pow(2, 3) = 2 * pow(2, 2) pow(2, 2) = 2 * pow(2, 1) pow(2, 1) = 2 So, the recursion reduces a function… Here’s the context stack when we entered the subcall pow(2, 2): Context: { x: 2, n: 2, at line… n: 1, at line 1 } pow(2, 1) Context: { x: 2, n: 2, at line 5 } pow(2, 2)… pow(2, 2) Context: { x: 2, n: 3, at line 5 } pow(2, 3) The execution of pow(2, 2) is

The browser ignores its contents, only checks for syntax validity, but we can access and use it in JavaScript… First, its content can be any valid HTML, even if it normally requires a proper enclosing tag.… The content becomes live (styles apply, scripts run etc) when we insert it into the document.… Inserting template.The template content is available in its content property as a DocumentFragment –… <template> content is considered “out of the document”, so it doesn’t affect anything.

Crossorigin policy.There’s a rule: scripts from one site can’t access contents of the other site.… Or, to be more precise, one origin (domain/port/protocol triplet) can’t access the content from another… For example, let’s take a script error.js that consists of a single (bad) function call:

For now, just remember the result of running the code: it shows Hello, then 1, then 2.… The content

Taking something and dragging and dropping it is a clear and simple way to do many things, from copying… Then JavaScript can access the contents of such files.… But if “take” it from its edge, then the ball suddenly “jumps” to become centered under the mouse pointer… In real-life we usually take one element and drop it onto another.… Speaking abstract, we take a “draggable” element and drop it onto “droppable” element.

Becomes… undefined NaN null 0 true and false 1 and 0 string Whitespaces (includes spaces, tabs… NaN null 0 true / false 1 / 0 string The string is read “as is”, whitespaces (includes spaces, tabs

Without options, this is a simple GET request, downloading the contents of the url.… we’ve already got the response with response.text(), then response.json() won’t work, as the body content… Please note, if the request body is a string, then Content-Type… as we’re going to send JSON, we use headers option to send application/json instead, the correct Content-Type… For Blob objects that type becomes the value of Content-Type.

Other pages that reference the same script will take it from the cache instead of downloading it, so… If src is set, the script content is ignored.

…But please note: the example above shows 1, then 2, and that’s all. It doesn’t show 3!… It starts the execution and returns the result of the first yield "2+2=?".… It may take time. That’s not a problem: the generator will wait.… For instance, here the yield of "2 + 2 = ?… The current line of the calling code is the line with generator.throw, labelled as (2).

Now let’s take the user variable as the “referent” and create a weak reference from it to the admin variable… Let’s delve into the details of what happened here: weakRefCache – is a higher-order function that takes… Return an anonymous function that takes the image name as an argument.… Now let’s take a closer look at the source code (tab index.js): Get the DOM-element of the “Start sending… It takes one argument – unregisterToken (the unregister token that was obtained when registering the

Solution 2: bind.Functions provide a built-in method bind that allows to fix this.… In the line (*) we take… Let’s take it a step further. We can bind not only this, but also arguments.… The call to mul.bind(null, 2)… creates a new function double that passes calls to mul, fixing null as the context and 2 as the first

Here we’ll see how to create new elements “on the fly” and modify the existing page content.… Creating the message.Creating the message div takes 3 steps:… We can append other nodes to it, but when we insert it somewhere, then its content is inserted instead… If we call it afterwards, the existing document content is erased.

The DOM allows us to do anything with elements and their contents, but first we need to reach the corresponding… So let’s see more navigation links that only take element nodes into account:… types of DOM elements, e.g. tables, provide additional properties and collections to access their content

There are no <easy-tabs>, <sliding-carousel>, <beautiful-upload>… Just think of any… Rendering in connectedCallback, not in constructor In the example above, element content

DOM (Document Object Model).The Document Object Model, or DOM for short, represents all page content… It takes the DOM specification and extends it with many additional properties and methods.

Users can’t see the page content till it downloads and runs:… Then it can see elements above it, and it doesn’t block the page content from showing:… The page content… The page content… So the user can read page content and get acquainted with the page immediately.