I have some HTML tags which have ng-clicks and ng-ifs. Inside the respective expressions, I make function calls and pass in parameters, some of which are literals (mostly just true or false). So I would like to add a comment as to what a literal means, but angular doesn't seem to be able to parse this correctly. (I realize passing literals is not the brightest idea but I would nevertheless like to know the answer)
<button class='someclass' ng-click='somefunction(val1, val2, true /* explanation for literal */)' > </button>
How do I add comments in angular expressions?
No, comments are not supported. Parser sees / as an mathematical operator (see source code) which expects primary expression after it: e.g. something starting with (, or [, etc. However there is no valid expression in javascript that can include * immediately after / character. So parser throws an exception: Token '*' not a primary expression.
While the Angular documentation doesn't explicitly say that JavaScript comments are not supported. I would assume they are not.
Angular Expressions are only a subset of some JavaScript (and some added features like filters).
Why can't you pass these comments as separate parameters instead of appending other parameters?
Even though you achieve doing this somehow it would be not very good design.
Related
I'm currently looking at regexs and emojis, and I'd like to use unicode property escapes to simplify the task
In https://unicode.org/reports/tr18/#Full_Properties, it lists a number of emoji properties such as Emoji and Emoji_Presentation etc.
Creating a regex using these patterns works:
const re = /\p{Emoji}/gu
The same page also lists RGI_Emoji, which is
The set of all emoji (characters and sequences) covered by ED-20, ED-21, ED-22, ED-23, ED-24, and ED-25.
or basic emojis, modifiers, etc, which seems to cover all use cases that I'm looking at.
However, creating a regex using this:
const re = /\p{RGI_Emoji}/gu
Gives a SyntaxError:
Uncaught SyntaxError: invalid property name in regular expression
The unicode page does mention that
Properties marked with * are properties of strings, not just single code points.
which RGI_Emoji is marked as. My knowledge of unicode isn't amazing, so I'm not sure of the proper way to use this.
Is it possible to use RGI_Emoji in a regex, and if so, what's the correct way to use it?
RGI_Emoji is not available in JavaScript yet.
It is mentioned on top of the Full Properties table that,
Properties marked with * are properties of strings, not just single code points.
Support for following sequence properties is being proposed in proposal-regexp-unicode-sequence-properties. The proposal is at stage 2 i.e. not part of the ECMAScript specification yet and hence not available.
RGI_Emoji
Basic_Emoji
Emoji_Keycap_Sequence
RGI_Emoji_Modifier_Sequence
RGI_Emoji_Flag_Sequence
RGI_Emoji_Tag_Sequence
RGI_Emoji_ZWJ_Sequence
To further confirm, check available \p{UnicodeBinaryPropertyName}'s in the latest ECMAScript specification. Only following properties of characters related to emoji's are available:
Emoji
Emoji_Component
EComp
Emoji_Modifier
EMod
Emoji_Modifier_Base
EBase
Emoji_Presentation
You'll have to form a regular expression with unicode ranges covering ED-20, ED-21, ED-22, ED-23, ED-24, and ED-25 unicode sets. Like suggested by #JosefZ in a comment.
This discussion may help JavaScript regular expression for Unicode emoji
The emoji properties were only added to UTS #18 relatively recently (mid 2020), and this involved a significant change in Unicode's properties model in that it involved formally defining for the first time properties of strings. RGI_Emoji is a binary-valued property of strings of characters. A potential issue for use of string properties in regex is that the set corresponding to a string property is potentially a vast number of strings. To avoid potential problems in existing implementations, UTS #18 allows for use of the syntax \m{Property_Name} for string properties. See https://www.unicode.org/reports/tr18/#Resolving_Character_Ranges_with_Strings for more information.
It's possible that the implementation you're using has not been fully updated for Rev. 21 of UTS #18, with support for all new properties, or that it requires you to use the \m syntax for string properties.
The online Unicode UnicodeSet utility does support enumerating string results of a regex using the RGI_Emoji property:
https://util.unicode.org/UnicodeJsps/list-unicodeset.jsp?a=%5Cp%7BRGI_Emoji%7D&g=&i=
I'm trying to evaluate an expression which contains power, in string as **. i.e. eval("(22**3)/12*6+3/2").The problem is Internet Explorer 11 does not recognizes this and throws syntax error. Which poly-fill I should use to overcome this? Right now I'm using Modernizr 2.6.2.
example equation would be,
((1*2)*((3*(4*5)*(1+3)**(4*5))/((1+3)**(4*5)-1)-1)/6)/7
((1*2)*((3*(4*5)*(1+3)**(4*5))/((1+3)**(4*5)-1)-1)/6)/7*58+2*5
(4*5+4-5.5*5.21+14*36**2+69/0.258+2)/(12+65)
If it is not possible to do this, what are the possible alternatives?
You cannot polyfill operators - only library members (prototypes, constructors, properties).
As your operation is confined to an eval call, you could attempt to write your own expression parser, but that would be a lot of work.
(As an aside, you shouldn't be using eval anyway, for very good reasons that I won't get into in this posting).
Another (hack-ish) option is to use a regular expression to identify trivial cases of x**y and convert them to Math.pow:
function detectAndFixTrivialPow( expressionString ) {
var pattern = /(\w+)\*\*(\w+)/i;
var fixed = expressionString.replace( pattern, 'Math.pow($1,$2)' );
return fixed;
}
eval( detectAndFixTrivialPow( "foo**bar" ) );
You can use a regular expression to replace the occurrences of ** with Math.pow() invocations:
let expression = "(22**3)/12*6+3/2"
let processed = expression.replace(/(\w+)\*\*(\w+)/g, 'Math.pow($1,$2)');
console.log(processed);
console.log(eval(processed));
Things might get complicated if you start using nested or chained power expressions though.
I think you need to do some preprocessing of the input. Here is how i would approach this:
Find "**" in string.
Check what is on the left and right.
Extract "full expressions" from left and right - if there is just a number - take it as is, and if there is a bracket - find the matching one and take whatever is inside as an expression.
Replace the 2 expressions with Math.pow(left, right)
You can use Babel online to convert javascript for IE 11.
Recently I found some interesting codes on a website.
<div class="inputArea">
<textarea type="text" id="textInput" class="chatInput lightBorder"></textarea>
</div>
<b>Send</b>
When I click the "Send" button (it's a hyperlink, but it looks like a button on the page") and it will fire the js code "sendMsg#.inputArea". What it does is to send a message in the textarea to the server. It acts like the sendMsg is a function and .inputArea is a parameter passed to that function. But it does not seem to follow the EMAC standard. However, it works. How is it possible? It now looks like black magic to me. Can someone explain how the # character works in the code?
Updated Answer
...now that you've shown what you think is "JavaScript code."
This isn't JavaScript code:
<b>Send</b>
<!-- Not JavaScript Code ----------------------^^^^^^^^^^^^^^^^^^ -->
That's just an attribute value on an element. (And an invalid one, a doesn't have a click attribute.) Presumably code in their JavaScript understands what to do with it. You're confusing that with an onclick attribute, which would (normally) contain JavaScript code.
Original Answer
You can't use # in a property name literal, variable name, or function name (collectively, an IdentifierName) in JavaScript.*
how to declare a special character in js
You can't. The characters allowed in IdentifierName are defined by the specification and are not extensible.
You can use any character you like as a property name (but not variable or function name), but not as a literal, only if you use brackets notation and a string, e.g.:
var obj = {"SendMsg#": "foo"};
console.log(obj["SendMsg#"]); // "foo"
* That said, JavaScript is very liberal about the characters you can use in IdentiferName, so while # isn't allowed, I couldn't absolutely guarantee there isn't some other Unicode character that looks a bit like it that's allowed. But I suspect not, as the Unicode page for # doesn't list any characters likely to be confused with #.
# isn't special at all in JavaScript, other than the fact that it isn't valid in identifiers - as in you can't use it for function and variable names. You can't declare custom operators in javascript, so unless you get to speak to the one who built that site, there's no way to tell what they do with # in strings.
On another note, many special characters are valid in JS, so you can name a function $, _ or even q̊̆̓̍u̐͂e̷̜r̤̻̫ͅy̎ if you want. But # isn't one of them.
Why doesn't this javascript regexp code work? According to the documentation it should:
Here's my String for parsing (it's the rails nested form information):
flex_table[flex_rows_attributes][0][flex_cells_attributes][0][id]
What I want are these sections, which may or may not be part of the string:
flex_rows_attributes, 0, flex_cells_attributes, 0
Here's my regular expression(as I mentioned, the javascript flavour):
flex_table((\[(\w+)\]\[(\d+)\])*)
I only get back the last of the two entries, but I want them both.
Does anyone know, what I am missing here?
^(?!flex_table\b).*$|(\[(\w+)\]\[(\d+)\])
Try this.Grab the captures.See demo.
http://regex101.com/r/hQ9xT1/26
I am trying to create my own javascript simple template function
I want to create a html page that will look like this
<p>
{{HELLO_WORLD}}
<br />
{{MY_NAME_IS}}
</p>
and than with javascript to replace anything that is in {{}}
with a json var that will look like this
{HELLO_WORLD: "Hello World!", MY_NAME_IS: "My name is"}
I am a little confused about the right method to do this.
the point is to make a multilanguage web site, that way I load the json for the desired language.
thank's.
JavaScript supports regular expression-based find-and-replace, with functions for the replacement. So you can do this:
myInputString.replace( /\{\{([^\}]*)\}\}/g, function( s, v ) { return myJSON[v] } );
To explain:
replace takes 2 arguments. The first is a regular expression object. In this case we build one inline using JavaScript's /expression/flags syntax. It looks for 2 opening braces (which need to be escaped because they have special meaning in regular expressions) followed by any characters which are not a closing brace, followed by 2 closing braces. The g means "global", so that it will match all cases rather than just the first one.
When a match is found, the function will be called. The first argument (I called it s) is the full matched string (like "{{abc}}"), the second (I called it v) is set to the first bit in brackets (like "abc").
In real code, you should add error checking (variables which don't exist), and possibly convert to lowercase / whatever.
Full details on replace are here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace