The code in question is here:
var $item = $(this).parent().parent().find('input');
What is the purpose of the dollar sign in the variable name, why not just exclude it?
A '$' in a variable means nothing special to the interpreter, much like an underscore.
From what I've seen, many people using jQuery (which is what your example code looks like to me) tend to prefix variables that contain a jQuery object with a $ so that they are easily identified and not mixed up with, say, integers.
The dollar sign function $() in jQuery is a library function that is frequently used, so a short name is desirable.
In your example the $ has no special significance other than being a character of the name.
However, in ECMAScript 6 (ES6) the $ may represent a Template Literal
var user = 'Bob'
console.log(`We love ${user}.`); //Note backticks
// We love Bob.
The dollar sign is treated just like a normal letter or underscore (_). It has no special significance to the interpreter.
Unlike many similar languages, identifiers (such as functional and variable names) in Javascript can contain not only letters, numbers and underscores, but can also contain dollar signs. They are even allowed to start with a dollar sign, or consist only of a dollar sign and nothing else.
Thus, $ is a valid function or variable name in Javascript.
Why would you want a dollar sign in an identifier?
The syntax doesn't really enforce any particular usage of the dollar sign in an identifier, so it's up to you how you wish to use it. In the past, it has often been recommended to start an identifier with a dollar sign only in generated code - that is, code created not by hand but by a code generator.
In your example, however, this doesn't appear to be the case. It looks like someone just put a dollar sign at the start for fun - perhaps they were a PHP programmer who did it out of habit, or something. In PHP, all variable names must have a dollar sign in front of them.
There is another common meaning for a dollar sign in an interpreter nowadays: the jQuery object, whose name only consists of a single dollar sign ($). This is a convention borrowed from earlier Javascript frameworks like Prototype, and if jQuery is used with other such frameworks, there will be a name clash because they will both use the name $ (jQuery can be configured to use a different name for its global object). There is nothing special in Javascript that allows jQuery to use the single dollar sign as its object name; as mentioned above, it's simply just another valid identifier name.
The $ sign is an identifier for variables and functions.
https://web.archive.org/web/20160529121559/http://www.authenticsociety.com/blog/javascript_dollarsign
That has a clear explanation of what the dollar sign is for.
Here's an alternative explanation: http://www.vcarrer.com/2010/10/about-dollar-sign-in-javascript.html
Dollar sign is used in ecmascript 2015-2016 as 'template literals'.
Example:
var a = 5;
var b = 10;
console.log(`Sum is equal: ${a + b}`); // 'Sum is equlat: 15'
Here working example:
https://es6console.com/j3lg8xeo/
Notice this sign " ` ",its not normal quotes.
U can also meet $ while working with library jQuery.
$ sign in Regular Expressions means end of line.
When using jQuery, the usage of $ symbol as a prefix in the variable name is merely by convention; it is completely optional and serves only to indicate that the variable holds a jQuery object, as in your example.
This means that when another jQuery function needs to be called on the object, you wouldn't need to wrap it in $() again. For instance, compare these:
// the usual way
var item = $(this).parent().parent().find('input');
$(item).hide(); // this is a double wrap, but required for code readability
item.hide(); // this works but is very unclear how a jQuery function is getting called on this
// with $ prefix
var $item = $(this).parent().parent().find('input');
$item.hide(); // direct call is clear
$($item).hide(); // this works too, but isn't necessary
With the $ prefix the variables already holding jQuery objects are instantly recognizable and the code more readable, and eliminates double/multiple wrapping with $().
No reason. Maybe the person who coded it came from PHP. It has the same effect as if you had named it "_item" or "item" or "item$$".
As a suffix (like "item$", pronounced "items"), it can signify an observable such as a DOM element as a convention called "Finnish Notation" similar to the Hungarian Notation.
I'll add this:
In chromium browser's developer console (haven't tried others) the $ is a native function that acts just like document.querySelector most likely an alias inspired from JQuery's $
Here is a good short video explanation: https://www.youtube.com/watch?v=Acm-MD_6934
According to Ecma International Identifier Names are tokens that are interpreted according to the grammar given in the “Identifiers” section of chapter 5 of the Unicode standard, with some small modifications. An Identifier is an IdentifierName that is not a ReservedWord (see 7.6.1). The Unicode identifier grammar is based on both normative and informative character categories specified by the Unicode Standard. The characters in the specified categories in version 3.0 of the Unicode standard must be treated as in those categories by all conforming ECMAScript implementations.this standard specifies specific character additions:
The dollar sign ($) and the underscore (_) are permitted anywhere in an IdentifierName.
Further reading can be found on: http://www.ecma-international.org/ecma-262/5.1/#sec-7.6
Ecma International is an industry association founded in 1961 and dedicated to the standardization of Information and Communication Technology (ICT) and Consumer Electronics (CE).
"Using the dollar sign is not very common in JavaScript, but
professional programmers often use it as an alias for the main
function in a JavaScript library.
In the JavaScript library jQuery, for instance, the main function $
is used to select HTML elements. In jQuery $("p"); means "select all
p elements". "
via https://www.w3schools.com/js/js_variables.asp
I might add that using it for jQuery allows you to do things like this, for instance:
$.isArray(myArray);
let $ = "Hello";
let $$ = "World!";
let $$$$$$$$$$$ = $ + " " + $$;
alert($$$$$$$$$$$);
This displays a "Hello World!" alert box.
As you can see, $ is just a normal character as far as JavaScript identifiers or variable names go. In fact you can use a huge range of Unicode characters as variable names that look like dollar or other currency signs!
Just be careful as the $ sign is also used as a reference to the jQuery namespace/library:
$("p").text("I am using some jquery");
// ...is the same as...
jQuery("p").text("I am using some jquery");
$ is also used in the new Template Literal format using string interpolation supported in JavaScript version ES6/2015:
var x = `Hello ${name}`;
This problem might be very simple but I find it a bit confusing & that is why I need help.
With relevance to this question I posted that got solved, I got a new issue that I just noticed.
Source code:
from PyQt5 import QtCore,QtWidgets
app=QtWidgets.QApplication([])
def scroll():
#QtCore.QRegularExpression(r'\b'+'cat'+'\b')
item = listWidget.findItems(r'\bcat\b', QtCore.Qt.MatchRegularExpression)
for d in item:
print(d.text())
window = QtWidgets.QDialog()
window.setLayout(QtWidgets.QVBoxLayout())
listWidget = QtWidgets.QListWidget()
window.layout().addWidget(listWidget)
cats = ["love my cat","catirization","cat in the clouds","catść"]
for i,cat in enumerate(cats):
QtWidgets.QListWidgetItem(f"{i} {cat}", listWidget)
btn = QtWidgets.QPushButton('Scroll')
btn.clicked.connect(scroll)
window.layout().addWidget(btn)
window.show()
app.exec_()
Output GUI:
Now as you can see I am just trying to print out the text data based on the regex r"\bcat\b" when I press the "Scroll" button and it works fine!
Output:
0 love my cat
2 cat in the clouds
3 catść
However... as you can see on the #3, it should not be printed out cause it obviously does not match with the mentioned regular expression which is r"\bcat\b". However it does & I am thinking it has something to do with that special foreign character ść that makes it a match & prints it out (which it shouldn't right?).
I'm expecting an output like:
0 love my cat
2 cat in the clouds
Researches I have tried
I found this question and it says something about this \p{L} & based on the answer it means:
If all you want to match is letters (including "international"
letters) you can use \p{L}.
To be honest I'm not so sure how to apply that with PyQT5 also still I've made some tries & and I tried changing the regex to like this r'\b'+r'\p{cat}'+r'\b'. However I got this error.
QString::contains: invalid QRegularExpression object
QString::contains: invalid QRegularExpression object
QString::contains: invalid QRegularExpression object
QString::contains: invalid QRegularExpression object
Obviously the error says it's not a valid regex. Can someone educate me on how to solve this issue? Thank you!
In general, when you need to make your shorthand character classes and word boundaries Unicode-aware, you need to pass the QRegularExpression.UseUnicodePropertiesOption option to the regex compiler. See the QRegularExpression.UseUnicodePropertiesOption reference:
The meaning of the \w, \d, etc., character classes, as well as the meaning of their counterparts (\W, \D, etc.), is changed from matching ASCII characters only to matching any character with the corresponding Unicode property. For instance, \d is changed to match any character with the Unicode Nd (decimal digit) property; \w to match any character with either the Unicode L (letter) or N (digit) property, plus underscore, and so on. This option corresponds to the /u modifier in Perl regular expressions.
In Python, you could declare it as
rx = QtCore.QRegularExpression(r'\bcat\b', QtCore.QRegularExpression.UseUnicodePropertiesOption)
However, since the QListWidget.findItems does not support a QRegularExpression as argument and only allows the regex as a string object, you can only use the (*UCP) PCRE
verb as an alternative:
r'(*UCP)\bcat\b'
Make sure you define it at the regex beginning.
for my $item (#array) {
if (index($item, '$n') != -1) {
print "HELLO\n";
}
}
Problem is: Perl critic gives below policy violation.
String may require interpolation at line 168, near '$item, '$n''. (Severity: 1)
Please advise how do I fix this?
In this case the analyzer either found a bug or is plain wrong in flagging your code.
Are you looking for a literal "$n" in $item, or for what $n variable evaluates to?
If you want to find the literal $n characters then there is nothing wrong with your code
If you expect $item to contain the value stored in $n variable then allow it to be evaluated,
if (index($item, $n) != -1)
If this is indeed the case but $n may also contain yet other escaped sequences or encodings which you need as literal characters (so to suppress their evaluation) then you may need to do a bit more, depending of what exactly may be in that variable.
In case you do need to find characters $ followed by n (what would explain a deliberate act of putting single quotes around a variable) you need to handle the warning.
For the particular policy that is violated see Perl::Critic::Policy::ValuesAndExpressions
This policy warns you if you use single-quotes or q// with a string that has unescaped metacharacters that may need interpolation.
To satisfy the policy you'd need to use double quotes and escape the $, for example qq(\$n). In my opinion this would change the fine original code segment into something strange to look at.
If you end up wanting to simply silence the warning see documentation, in Bending The Rules
A comment. The tool perlcritic is useful but you have to use it right. It's a static code analyzer and it doesn't know what your program is doing, so to say; it can catch bad practices but can't tell you how to write programs. Many of its "policies" are unsuitable for particular code.
The book that it is based on says all this very nicely in its introduction. Use sensibly.
When I look at the question where this comes from it appears that you are looking for index at which substrings were matched, so you need the content of $n variable, not literal "$n". Then perlcritic identified a bug in the code, good return for using it!
Im sure of paper.path("path string") .But some examples use path method with no arguments.
I looked into the docs paper.path, its saying the path string is optional, but it hasn't said what happens when there is no path string.
You're correct that it allows empty paths. The definition from W3C is:
svg-path:
wsp* moveto-drawto-command-groups? wsp*
allowing any amount of white space surrounding zero or one of the moveto/drawto command groups.
From that W3C documentation page:
Note that the BNF allows the path ‘d’ attribute to be empty. This is not an error, instead it disables rendering of the path.
In other words, it's a path with no elements in it. Without this, you'd probably have to have some kludge like m 0 0 if you wanted a path to do nothing.
i have something like
<s:link view="/member/index.xhtml" value="My News" propagation="none"/>
<s:link view="/member/index.xhtml" value="#{msg.myText}" propagation="none"/>
where the value of myText in the messages.properties is
myText=My News
The first line of the example works fine and replaces the text to "My News", but the second that uses a value from the resource bundle escapes the ambersand, too "My News".
I tried also to use unicode escape sequences for the ambersand and/or hash with My\u0026\u0023160;News, My\u0026#160;News and My\u0026nbsp;News in the properties file without success.
(Used css no-wrap instead of the previous used xml encoding, but would be interested anyway)
EDIT - Answer to clarified question
The first is obviously inline, so interpreter knows that this is safe.
The second one comes from external source (you are using Expression Language) and as such is not safe and need to be escaped. The result of escaping would be as you wrote, basically it will show you the exact value of HTML entity.
This is related to security (XSS for example) and not necessary i18n.
Previous attempt
I don't quite know what you are asking for but I believe it is "how to display it?".
Most of the standard JSF controls contain escape attribute that if set to false won't escape the text. Unfortunately it seems that you are using something like SeamTools which does not have this attribute.
Well, in this case there is not much to be done. Unless you could use standard control, maybe you should go and try to actually save your properties file as Unicode (UTF-16 BigEndian in fact) and simply put valid Unicode non-breaking space character. Theoretically that should work; Unicode-encoded properties files are supported in latest version of Java (although I cannot recall if it was Java SE 5 or Java SE 6)...