What are escape tags in html?
Are they " < > to represent " < >?
And how do these work?
Is that hex, or what is it?
How is it made, and why aren't they just the characters themselves?
Here are some common entities. You do not need to use the full code - there are common aliases for frequently used entities. For example, you can use < and > to indicate less than and greater than symbols. & is ampersand, etc.
EDIT: That should be - < > and &
EDIT: Another common character is   which is often used to represent tabs in <code> segments
How do these work?
Anything &#num; is replaced with character from ASCII table, matching that num.
Is that hex, or what is it?
It's not hex, the number represents characters number in decimal in ASCII table. Check out ASCII table. Check Dec and HTML columns.
Why aren't they just the characters themselves?
Look at this example:
<div>Hey you can use </div> to end div tag!</div>
It would mess up the interpreter. It's a bad example, but you got the idea.
Why you can't use escape characters like in programming languages?
I don't have exact answer to that. But html same as xml is a markup language and not programming language and answer probably lies within history of how markup languages become what they are now.
No, it's not hex, it's decimal. Hex equivalent is < But one usually uses < (less-than) for < and > for > instead.
Here is the complete reference of html entities:
Complete HTML Entities
It is use for correct character formatting
HTML has a set of special characters which browsers recognize as part of the HTML language itself. For example, browsers know that when they encounter a < character in the HTML code, they are to interpret it as a beginning of a tag. > is one of an example of reserved character. Therefore use html character to avoid any problem and for correct practice also
Those escapes are decimal ascii escapes. You can see the values here. Take a look at the HTML column.
Related
This question already has answers here:
Regex to match only letters
(20 answers)
Closed 8 years ago.
I'm trying to create a regex for a HTML5 input so a user can only insert alpha characters that may be in a name. So characters from a-z, but also including ö,ü,â,æ ... and so on whilst also allowing whitespace and hyphens .
I have played around with some pattens but nothing seems to work correctly, this is what I have so far: <input type="text" name="firstname" pattern="[a-zA-Z\x7f-\xff] " title="">
Does anyone have a quick answer for this?
Since the HTML5 pattern attribute uses the same regex syntax as JavaScript, there is no simple way to refer to all alphabetic characters. You would need to write a rather huge expression (and to update it as new alphabetic characters are added to Unicode). You would need to start from the Unicode character database and the definition of General Category of characters there, or rely on someone having done that for you.
However, for your practical purposes, testing for “alpha characters that may be in a name” is even more complex. There are non-alphabetic characters used in names, such as left single quotation mark (‘) in addition to normal quotation mark (’), and who knows what characters there might be? If this is about people’s real names, it is very difficult to impose restrictions that do not discriminate. If this is about user names in a system, for example, you can define the repertoire as you like, but [a-zA-Z\x7f-\xff] does not look adequate (it includes some control characters and some non-alphabetic characters and excludes many Latin letters commonly used in Europe).
There is a very simple method to apply all you RegEx logic(that one can apply easily in English) for any Language using Unicode.
For matching a range of Unicode Characters like all Alphabets [A-Za-z] we can use
[\u0041-\u005A] where \u0041 is Hex-Code for A and \u005A is Hex Code for Z
'matchCAPS leTTer'.match(/[\u0041-\u005A]+/g)
//output ["CAPS", "TT"]
In the same way we can use other Unicode characters or their equivalent Hex-Code according to their Hexadecimal Order (eg: \u0100–\u017FF) provided by unicode.org
Try: [À-ž] as an example of Range. Modify your Range according to your requirement.
It will match all characters between À and ž.
Sample regEx would be
/[A-Za-zÀ-ž\-\s]+/
For more Ref: Latin Unicode Character
I would like to paste into my HTML code a phrase
"<car>"
and I would like that this word "car" will be between <>. In some text will be
"<car>"
and this is not a HTML expression. The problem is that when I put it the parser think that this is the HTML syntax how to avoid it. Is there any expression which need to be between this?
replace < by < and > by >
Live on JSFiddle.
< and > are special characters, more special characters in HTML you can find here.
More about HTML entities you can find here.
use > for > and < for <
$gt;car<
you need to use special character .. To know more about Special Character link here
CODE:
<p>"<car >"</p>
OUTPUT:
"<car>"
< = < less than
> = > greater than
The same applies for XML too. Take a look here, special characters for HTML.
If you really want LESS THAN SIGN “<” to appear visibly in page content, write it as &, so that it will not be treated as starting a tag. Ref.: 5.3.2 Character entity references in HTML 4.01.
So you would write
<car>
If you like, you can write “>” as > for symmetry, but there is no need to.
But if you really want to put something in angle brackets, e.g. using a mathematical notation, rather than a markup notation (as in HTML and XML), consider using U+27E8 MATHEMATICAL LEFT ANGLE BRACKET “⟨” and U+27E9 MATHEMATICAL RIGHT ANGLE BRACKET “⟩”. They cause no problems to HTML markup, as they are not markup-significant. If you don’t know how to type them in your authoring environment, you can use character references for them:
⟨car⟩
This would result in ⟨car⟩, though as always with less common special characters, you would need to consider character (font) problems.
You can use the "greater than" and "less than" entities:
<car>
The W3C, the organization responsible for setting web standards, has some pretty good documentation on HTML entities. They consist of an ampersand followed by an entity name followed by a semicolon (&name;) or an ampersand followed by a pound sign followed by an entity number followed by a semicolon (&#number;). The link I provided has a table of common HTML entities.
I am currently creating a webpage to teach others HTML. In my HTML document, I want to make a paragraph like, "Start with html, and end with /html". The html and /html should have <> tags around them, but I don't know how to do this! (this is my question) The document just leaves html and /html (with <> around them) out. How do I make sure that the document leaves it in?
Thank you.
Use HTML entities
To write the characters < and > use < and >
This gives you:
<html> and </html>
Rendered as:
<html> and </html>
This is called HTML Entities. A more complete list can be found here or on wikipedia.
In HTML, there is a standard set of 252 named character entities for
characters - some common, some obscure - that are either not found in
certain character encodings or are markup sensitive in some contexts
(for example angle brackets and quotation marks). Although any Unicode
character can be referenced by its numeric code point, some HTML
document authors prefer to use these named entities instead, where
possible, as they are less cryptic and were better supported by early
browsers. Character entities can be included in an HTML document via
the use of entity references, which take the form &EntityName;, where
EntityName is the name of the entity. For example, —, much like
— or —, represents U+2014: the em dash character "—" even
if the character encoding used doesn't contain that character.
Use amp codes (HTML Entities)!
<p><html></p>
You can use the HTML entities: > for >, < for <.
If you want to display HTML tags replace all < and > with < and <
Example: <HTML>
use < for < and >for >
Yes, I've googled it, and surprisingly got confusing answers.
One page says that < > & " are the only reserved characters in (X)HTML. No doubt, this makes sense.
This page says < > & " ' are the reserved characters in (X)HTML. A little confusing, but okay, this makes sense too.
And then comes this page which says < > & " © ° £ and non-breaking space ( ) are all reserved characters in (X)HTML. This makes no sense at all, and pretty much adds to my confusion.
Can someone knowledgeable, who actually do know this stuff, clarify which the reserved characters in (X)HTML actually are?
EDIT: Also, should all the reserved characters in code be escaped when wrapped in <pre> tag? or is it just these three -- < > & ??
The XHTML 1.0 specification states at http://www.w3.org/TR/2002/REC-xhtml1-20020801/#xhtml:
XHTML 1.0 [...] is a reformulation of the three HTML 4 document types as
applications of XML 1.0 [XML].
The XML 1.0 specification states at http://www.w3.org/TR/2008/REC-xml-20081126/#syntax:
Character Data and Markup: Text consists of intermingled character
data and markup. [...] The ampersand character (&) and the left angle
bracket (<) MUST NOT appear in their literal form, except when used as
markup delimiters, or within a comment, a processing instruction, or a
CDATA section. If they are needed elsewhere, they MUST be escaped
using either numeric character references or the strings "&" and
"<" respectively. The right angle bracket (>) may be represented
using the string ">", and MUST, for compatibility, be escaped
using either ">" or a character reference when it appears in the
string "]]>" in content, when that string is not marking the end of
a CDATA section.
This means that when writing the text parts of an XHTML document you must escape &, <, and >.
You can escape a lot more, e.g. ü for umlaut u. You can as well state that the document is encoded in for example UTF-8 and write the byte sequence 0xc3bc instead to get the same umlaut u.
When writing the element parts (col. "tags") of the document, there are different rules. You have to take care of ", ' and a lot of rules concerning comments, CDATA and so on. There are also rules which characters can be used in element and attribute names. You can look it up in the XML specification, but in the end it comes down to: for element and attribute names, use letters, digits and "-"; do not use "_". For attribute values, you must escape & and (depending on the quote style) either ' or ".
If you use one of the many libraries to write XML / XHTML documents, somebody else has already taken care of this and you just have to tell the library to write text or elements. All the escaping is done the in the background.&
Only < and & need to be escaped. Inside attributes, " or ' (depending on which quote style you use for the attribute's value) needs to be escaped, too.
<a href="#" onclick='here you can use " safely'></a>
By writing "(X)HTML", you are asking (at least) two different questions.
By the HTML rules, with "HTML" meaning any HTML version up to and including HTML 4.01, only "<" and "&" are reserved. The rules are somewhat complex. They should not not appear literally except in their syntactic use in tags, entity references, and character references. But by the formal rules, they may appear literally e.g. in the context "A & B" or "A < B" (but A&B be formally wrong, and so would A<B).
The XHTML rules, based on XML, are somewhat stricter, simpler: "<" and "&" are unconditionally reserved.
The ASCII quotation mark " and the ASCII apostrophe ' are not reserved, except in the very specific sense that a quoted attribute value must not literally contain the character used as quote, i.e. in "foo" the string foo must not contain " as such and in 'foo' the string foo must not contain ' as such.
The characters < > & " are reserved by XML format.
It means that you can use < and > chars only to define tags (<mytag></mytag>).
Double quotes (") are used to define values of attributes (<mytag attribute="value" />)
Ampersand (&) is used to write entities (& is used when you actually want to write ampersand, NOT &). Also, when you write url in your XML document, you should use &, not just &: www.aaa.com?a=1&b=2 - is wrong; www.aaa.com?a=1&b=2 - is good!
XHTML is based on XML, so what I have wrote applies to XHTML.
© ° £ - These are not reserved chars. These are entities defined specifically for XHTML, not for XML.
In XML you can simply write ©. In XHMTL you can also simply write ©, or use entity ©, or numeric entity &00A9;.
In addition to the other answers, it might help to know that there are also forbidden characters: all control characters in ASCII and ISO-8859-1 except TAB, LF, and CR.
https://www.w3.org/MarkUp/html3/specialchars.html
I am having trouble understanding how escaping works inside html tag attribute values that are javascript.
I was lead to believe that you should always escape & ' " < > . So for javascript as an attribute value I tried:
It doesn't work. However:
and
does work in all browsers!
Now I am totally confused. If all my attribute values are enclosed in double quotes, does this mean I do not have to escape single quotes? Or is apos and ascii 39 technically different characters? Such that javascript requires ascii 39, but not apos?
There are two types of “escapes” involved here, HTML and JavaScript. When interpreting an HTML document, the HTML escapes are parsed first.
As far as HTML is considered, the rules within an attribute value are the same as elsewhere plus one additional rule:
The less-than character < should be escaped. Usually < is used for this. Technically, depending on HTML version, escaping is not always required, but it has always been good practice.
The ampersand & should be escaped. Usually & is used for this. This, too, is not always obligatory, but it is simpler to do it always than to learn and remember when it is required.
The character that is used as delimiters around the attribute value must be escaped inside it. If you use the Ascii quotation mark " as delimiter, it is customary to escape its occurrences using " whereas for the Ascii apostrophe, the entity reference ' is defined in some HTML versions only, so it it safest to use the numeric reference ' (or ').
You can escape > (or any other data character) if you like, but it is never needed.
On the JavaScript side, there are some escape mechanisms (with \) in string literals. But these are a different issue, and not relevant in your case.
In your example, on a browser that conforms to current specifications, the JavaScript interpreter sees exactly the same code alert('Hello');. The browser has “unescaped” ' or ' to '. I was somewhat surprised to hear that ' is not universally supported these days, but it’s not an issue: there is seldom any need to escape the Ascii apostrophe in HTML (escaping is only needed within attribute values and only if you use the Ascii apostrophe as its delimiter), and when there is, you can use the ' reference.
' is not a valid HTML reference entity. You should escape using '