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In JavaScript, the textual data is stored as strings.… The syntax is: func`string`.… String length.The length property has the string length:… If pos is negative, then it’s counted from the end of the string.… and end of the string. str.repeat(n) – repeats the string n times.

Advanced knowledge The section goes deeper into string internals.… As we already know, JavaScript strings are based on Unicode: each character is represented by a byte… JavaScript allows us to insert a character into a string by specifying its hexadecimal Unicode code with… We actually have a single symbol in each of the strings above, but the length property shows a length… Takeaway: splitting strings at an arbitrary point is dangerous We can’t just split a string

regexps in-depth. str.match(regexp).The method str.match(regexp) finds matches for regexp in the string… When the first argument of replace is a string, it only replaces the first match.… whole match $` inserts a part of the string before the match $' inserts a part of the string after… The main use case for replaceAll is replacing all occurrences of a string.… Unlike previous methods, it’s called on a regexp, not on a string.

The pattern ^Mary means: “string… Similar to this, we can test if the string ends with snow using snow$:… Testing for a full match.Both anchors together ^...$ are often used to test whether or not a string fully… Let’s check whether or not a string is a time in 12:34 format.… The whole string must be exactly in this format.

The built-in eval function allows to execute a string of code.… A string… That’s usually safe, but not if eval is used, as local variables may be accessed from eval’ed code string… It creates a function from a string, also in the global scope. So it can’t see local variables.… Summary.A call to eval(code) runs the string of code and returns the result of the last statement.

String Conversion.String conversion happens when we need the string form of a value.… We can also call the String(value) function to convert a value to a string:… If the remaining string is empty, the result is 0. Otherwise, the number is “read” from the string.… String Conversion – Occurs when we output something. Can be performed with String(value).… An empty string becomes 0. An error gives NaN.

So it’s a special character in regexps (just like in regular strings).… The example below looks for a string "g()":… The reason is that backslashes are “consumed” by a string.… So new RegExp gets a string without backslashes. That’s why the search doesn’t work!… When passing a string to new RegExp, we need to double backslashes \\, cause string quotes consume one

module that implements searching for regexps) comes across \b, it checks that the position in the string… There are three different positions that qualify as word boundaries: At string start, if the first string… Between two characters in the string, where one is a word character \w and the other is not.… At string end, if the last string character is a word character \w.… In the string Hello, Java!

There exist only numeric and string conversions.… They’re called “hints”, as described in the specification: "string" For an object-to-string… Then "2" * 2 becomes 2 * 2 (the string is converted to number).… Binary plus will concatenate strings in the same situation, as it gladly accepts a string:… There are 3 types (hints) of it: "string" (for alert and other operations that need a string

JavaScript allows us to work with primitives (strings, numbers, etc.) as if they were objects.… There are 7 primitive types: string, number, bigint, boolean, symbol, null and undefined.… For instance, there exists a string method str.toUpperCase() that returns a capitalized str.… Here’s what actually happens in str.toUpperCase(): The string str is a primitive.… That method runs and returns a new string (shown by alert).

If the first character from the first string is greater (or less) than the other string’s, then the first… string is greater (or less) than the second.… Repeat until the end of either string. If both strings end at the same length, then they are equal.… Otherwise, the longer string is greater.… The first string is greater.

) – append nodes or strings at the end of node, node.prepend(...nodes or strings) – insert nodes or strings… at the beginning of node, node.before(...nodes or strings) –- insert nodes or strings before node, node.after… (...nodes or strings) –- insert nodes or strings after node, node.replaceWith(...nodes or strings) –-… (...nodes or strings) – insert into node, at the beginning, node.before(...nodes or strings) –- insert… Text strings are inserted “as text”.

There are no networking methods that require exactly a URL object, strings are good enough.… the string conversion, that turns a URL object into a string with full URL.… As of now, URL objects are often more convenient, but strings can still be used as well.… In many cases using a string makes the code shorter.… If we use a string though, we need to encode/decode special characters manually.

In JavaScript, they are available via the RegExp object, as well as being integrated in methods of strings… They play the same role as quotes for strings.… syntaxes is that pattern using slashes /.../ does not allow for expressions to be inserted (like string… The method str.match(regexp) finds all matches of regexp in the string str.… Full information about the methods is given in the article Methods of RegExp and String. Summary.

Let’s say we have a complex object, and we’d like to convert it into a string, to send it over a network… Naturally, such a string should include all important properties.… The value of meetup.date is a string, not a Date object.… How could JSON.parse know that it should transform that string into a Date?… JSON supports plain objects, arrays, strings, numbers, booleans, and null.

What if the binary data is actually a string? For instance, we received a file with textual data.… The built-in TextDecoder object allows one to read the value into an actual JavaScript string, given… TextEncoder.TextEncoder does the reverse thing – converts a string… It has two methods: encode(str) – returns Uint8Array from a string. encodeInto(str, destination) – encodes

For example, a string or a number. There are eight basic data types in JavaScript.… We’ll cover strings more thoroughly in the chapter Strings.… There’s only one type: string.… for strings.… Returns a string with the name of the type, like "string".

We can use the contents of capturing groups (...) not only in the result or in the replacement string… We need to find quoted strings: either single-quoted '...' or a double-quoted "...… ['"], but it would find strings with mixed quotes, like "...' and '...".… That would lead to incorrect matches when one quote appears inside other ones, like in the string "… Don’t mess up: in the pattern \1, in the replacement: $1 In the replacement string we use

For instance, strings are also iterable.… String is iterable.Arrays and strings are most widely used built-in iterables.… We’ll iterate over a string in exactly the same way as for..of, but with direct calls.… Built-in iterables like strings or arrays, also implement Symbol.iterator.… String iterator knows about surrogate pairs.

fileParts – is an array of Blob/BufferSource/String… values. fileName – file name string. options – optional object: lastModified – the timestamp (integer… read the data in binary format ArrayBuffer. readAsText(blob, [encoding]) – read the data as a text string… we can call them directly, without reading. readAsText – for text files, when we’d like to get a string… FileReader objects can read from a file or a blob, in one of three formats: String (readAsText).

By specification, only two primitive types may serve as object property keys: string type, or symbol… Otherwise, if one uses another type, such as number, it’s autoconverted to string.… Until now we’ve been using only strings. Now let’s explore symbols, see what they can do for us.… Symbols don’t auto-convert to a string Most values in JavaScript support implicit conversion… to a string.

Seven of them are called “primitive”, because their values contain only a single thing (be it a string… They can be any strings or symbols (a special type for identifiers, to be covered later).… Other types are automatically converted to strings.… That’s usually a quoted string.… They store properties (key-value pairs), where: Property keys must be strings or symbols (usually strings

The first thing to do is to locate quoted strings, and then we can replace them.… The regular expression engine tries to find it at the zero position of the source string a "witch… It tries to see if the rest of the subject string conforms to .+".… But there’s a problem: the string has finished, there are no more characters!… There are no more quotes in the rest of the string is one, so no more results.

So we can operate both on the full class string… Setting elem.style.width="100px" works the same as if we had in the attribute style a string… Instead of delete elem.style.display we should assign an empty string to it: elem.style.display = "… To set the full style as a string, there’s a special property style.cssText:… An empty string or no argument means the element itself.

Blob consists of an optional string type (a MIME-type usually), plus blobParts – a sequence of other… Blob objects, strings and BufferSource.… blobParts is an array of Blob/BufferSource/String… This behavior is similar to JavaScript strings: we can’t change a character in a string, but we can make… a new corrected string.

one is converted to a string too.… Here, the first operand is a string, the compiler treats the other two operands as strings too.… The binary + is the only operator that supports strings in such a way.… The need to convert strings to numbers arises very often.… For example, if we are getting values from HTML form fields, they are usually strings.

The contents of every group in the string: Optional groups.Even… And here’s a more complex match for the string ac:… ) and input (source string):… We can also use parentheses contents in the replacement string in str.replace: by the number $n or the… We also can’t reference such parentheses in the replacement string.

number for both floating-point and integer numbers, bigint for integer numbers of arbitrary length, string… for strings, boolean for logical values: true/false, null – a type with a single value null, meaning… The binary plus + concatenates strings.… And if any of the operands is a string, the other one is converted to string too:… Greater/less comparisons compare strings character-by-character, other types are converted to a number

Their values are always strings.… We can assign anything to an attribute, but it becomes a string.… DOM properties are typed.DOM properties are not always strings.… Quite rarely, even if a DOM property type is a string, it may differ from the attribute.… Properties Attributes Type Any value, standard properties have types described in the spec A string

It’s a byte array though, not a string. To create a string, we need to interpret these bytes.… What if we need binary content instead of a string? That’s even simpler.… At the end we have the result (as a string

For instance, CSS\d matches a string CSS with a digit after it:… In the beginning of the chapter we saw how to make a number-only phone number from a string like +7(903… An alternative, shorter way is to find non-digits \D and remove them from the string:… For us strings 1-5 and 1 - 5 are nearly identical.… Unicode encoding, used by JavaScript for strings, provides many properties for characters, like: which

Bonus: Object.prototype.toString for the type.We already know that plain objects are converted to string… use {}.toString.call instead of instanceof for built-in objects when we want to get the type as a string… Summary.Let’s summarize the type-checking methods that we know: works for returns typeof primitives string… {}.toString primitives, built-in objects, objects with Symbol.toStringTag string instanceof objects

The items are sorted as strings by default.… Literally, all elements are converted to strings for comparisons.… Use localeCompare for strings Remember strings comparison algorithm?… It splits the string into an array by the given delimiter delim.… It creates a string of arr items joined by glue between them.

(which we will see later in this chapter). toString(base).The method num.toString(base) returns a string… The method toFixed(n) rounds the number to n digits after the point and returns a string representation… They “read” a number from a string until they can’t.… It specifies the base of the numeral system, so parseInt can also parse strings of hex numbers, binary… numbers directly in hex (0x), octal (0o) and binary (0b) systems. parseInt(str, base) parses the string

The typical symptom – a regular expression works fine sometimes, but for certain strings it “hangs”,… Example.Let’s say we have a string, and we’d like to check if it consists of words \w+ with an optional… Although, on certain strings it takes a lot of time.… The next character in the pattern is the string end $.… *$ in the string An input that hangs!.

The major difference from other ways we’ve seen is that the function is created literally from a string… But new Function allows to turn any string into a function.… Imagine that we must create a function from a string.

JavaScript uses Unicode encoding for strings.… must be considered only together (so-called “surrogate pair”, you can read about them in the article Strings… And, as it happens with strings, that may lead to odd results.… Unlike strings, regular expressions have flag u that fixes such problems.

Where’s the code that generates the string… Primitives.The most intricate thing happens with strings, numbers and booleans.… try to access their properties, temporary wrapper objects are created using built-in constructors String… For instance, if we add a method to String.prototype, it becomes available to all strings:

For the start, let’s find the price from the string like 1 turkey costs 30€.… In our string… Negative lookahead.Let’s say that we want a quantity instead, not a price from the same string.

URL – the URL to request, a string, can be URL object. async – if explicitly set to false, then the request… 200, 404, 403 and so on, can be 0 in case of a non-HTTP failure. statusText HTTP status message (a string… , "text" – get as string, "arraybuffer" – get as ArrayBuffer (for binary data, see… They exist for historical reasons, to get either a string or XML document.… Or, if we like JSON more, then JSON.stringify and send as a string.

Strings only.Please note that both key and value must be strings.… If they were any other type, like a number, or an object, they would get converted to a string automatically… Both key and value must be strings. The limit is 5mb+, depends on the browser. They do not expire.

As we can see, unlike objects, keys are not converted to strings… this is treating map as a plain JavaScript object, so it implies all corresponding limitations (only string… String as a key in Object is fine, but we can’t use another Object as a key in Object.… As visitsCountObj is an object, it converts all Object keys, such as john and ben above, to same string

Let’s say we have a string like +7(903)-123-45-67 and want to find all numbers in it.… Let’s return to the string

For instance, here we use the spread syntax to turn the string into array of characters:… So, for a string, for..of returns characters and ...str becomes "H","e","l"… For this particular task we could also use Array.from, because it converts an iterable (like a string

POST, body – the request body, one of: a string (e.g.… Please note, if the request body is a string… object with request headers (not any header is allowed), body – the data to send (request body) as string

Parameters: func|code Function or a string… For historical reasons, a string of code can be passed, but that’s not recommended. delay The delay before… If the first argument is a string… But using strings

versus primitives is that objects are stored and copied “by reference”, whereas primitive values: strings… Let’s start with a primitive, such as a string.… As a result we have two independent variables, each one storing the string

The flag y allows to perform the search at the given position in the source string.… E.g. we have a code string let varName = "value", and we need to read the variable name from

new Date(datestring) If there is a single argument, and it’s a string… Date.parse from a string.The method Date.parse(str) can read a date from a string.… The string format should be: YYYY-MM-DDTHH:mm:ss.sssZ, where: YYYY-MM-DD – is the date: year-month-day… The call to Date.parse(str) parses the string in the given format and returns the timestamp (number of

A string can not become a prototype. That’s why an assignment a string to __proto__ is ignored.… But in other cases we may be storing objects instead of strings in obj, and then the prototype will indeed