I have a problem with regex in javascript. for example i have recorver list of programming language to my csv file. what i want is i must replace all the programming that have newline inside the double quote, and also the double quote with a space the sample output below. the output must be Ruby on Rails and C++ without double quote and newline.
SAMPLE OUTPUT
PYTHON
PHP
"Ruby on
Rails"
"C+
+"
I TRIED THIS CODE
how will i include also the new line inside the double quote
str.replace(/['"]+/g, ' ');
The difficulty with this question is that you have to find a way to know if the newline sequence must be replaced with a space or an empty string.
When the newline sequence is between word-boundaries, this means that there are a word character [a-zA-Z0-9_] before and after it (like in on\nRails). In this case it seems logical to send a space.
In other cases like C+\n+ or any other string that starts or ends with a newline, you can return an empty string.
txt = txt.replace(/"([^"]*)"/g, function (m,g) {
return g.replace(/\b([\r\n]+)\b|[\r\n]+/g, function(n,h) {
return h ? ' ' : '';
});
});
Let me know if you find other (interesting) edge cases.
Related
I'm receiving this string from an external source (with a single backslash):
"Spool10072098_\P_18005389.txt"
Javascript completely ignoring "\", but I still need to get the string completely as I need to get the substring after it, P_18005389.txt in this case.
So my question is, how to get the substring after \ ?
Try String.raw method:
var example = String.raw`Spool10072098_\P_18005389.txt`;
console.log(example.split('\\')[1])
In your code, you need to escape a backslash, like this:
/* The memory will read "Spool10072098_\P_18005389.txt": */
var x = 'Spool10072098_\\P_18005389.txt';
Then you can split the string using split.
const second_part = x.split('\\')[1];
As you told us, the string you get from some other source than your source code, has only one backslash. That's okay, then the string in the memory contains the one backslash as you wanted.
Backslash is used in source code to mark up various special characters. That's why, if you want it to appear in your string, you need to escape it using another backslash.
For example:
"\n" /* will return a string containing a newline */
"\t" /* will return a string containing a tabulator */
"\\" /* will return a string containing a single \ character */
I have a program (written in Clojure) that injects some JS code into a JS function, then evaluates it via Nashorn. I have no control over the code passes (it may contain quotes, simple quotes...).
It looks like this :
;; Clojure
(eval-str (str "print(evaluateCode(\"" s " \"))"))
// equivalent code in pseudo-js just for those not reading Clojure fluently
evalJS("println(evaluateCode(" + arbitraryJS + "))")
The evaluateCode function is already loaded.
// already loaded in Nashorn
function evaluateCode(code) {
// do something with the code
//...
eval(code);
}
This works fine for simple programs, ex. if arbitraryJS = "var a=123; print(a); return a;".
But as soon as the program contains quotes, it breaks. ex. "var a = 123; print("a is now", a);"
Note : the actual code is there.
You need to escape the string. place a \ before every ".
If you need the \ itself use it double \\
Sorry, I am not allowed to comment yet... :/
I would suggest to escape the quotes and backslashes. I would go for single quotes as JS string delimiters, as in Clojure you are bound to use double quotes for delimiting strings:
;; Clojure
(eval-str (str "print(evaluateCode('"
(clojure.string/replace s #"(['\\\\])" "\\\\$1")
"'))"))
The find and replace patterns each have four backslashes. As in Clojure backslash is an escape character, they actually denote only two backslashes. In regular expressions backslash is also an escape character, so in the end they just denote one, literal backslash each. So this means "prefix any occurrence of backslash or quote with a backslash."
You shouldn't worry about comments and templates and such, as the escape characters only exist in Clojure (after the replace), but are resolved the moment the complete string is parsed by the Javascript engine. The evaluateCode function will never see the escape characters, but the plain value of s.
Example
;; Clojure
(def s "a = 'test'; // 'test' used here")
(eval-str (str "print(evaluateCode('"
(clojure.string/replace s #"(['\\\\])" "\\\\$1")
"'))"))
This will evaluate to:
(eval-str "print(evaluateCode('a = \\'test\\'; // \\'test\\' used here'))")
Note that the backslashes are doubled in the above representation, but that is because Clojure needs that. The actual string only has single occurrences of the backslashes. If instead of calling eval-str, you would call println with the same argument, you would get this output:
print(evaluateCode('a = \'test\'; // \'test\' used here'))
That is the string interpreted by the Javascript engine, and so it interprets the backslashes as escape characters, passing the clean string to evaluateCode.
So if evaluateCode looked like this:
function evaluateCode(code) {
alert(code);
}
It would produce this alert:
a = 'test'; // 'test' used here
So, the escaping backslashes are not there at all in Javascript. It will see the exact same value as the Clojure symbol s represents.
In the after end I used the Apache Commons Lang StringUtils since the other solutions did not work. See it here.
through queries to a Database I am retrieving such data that I previously inserted through HTML textarea or input. When I get the response from my DB , in a JSON object the text field looks like this :
obj : {
text : [some_text] ↵ [some_text]
}
I tried to replace with this function :
string_convert = function(string){
return string.replace("↵",'<br>')
.replace('&crarr','<br>')
.replace('/[\n\r]/g','<br>');
}
I have to show this string in HTML ,but it does not seems to work. I'm using UTF-8
Any advice?
The problem you have is that you have enclosed your regex in quotes. This is incorrect.
.replace('/[\n\r]/g','<br>');
^ ^
remove these two quotes
The quotes are unnecessary because the regex is already delimited by the slashes.
By putting quotes in there, you've actually told it that you want to replace a fixed string rather than a regular expression. The fixed string may look like an expression, but with the quotes, it will just be seen as a plain string.
Remove the quotes and it will be seen as an expression, and it will work just fine.
One other thing, though -- in order to make your regex work perfectly, I'd also suggest modifying it slightly. As it stands, it will just replace all the \n and \r characters with <br>. But in some cases, they may come together as a \r\n pair. This should be a single line break, but your expression will replace it with two <br>s.
You could use an expression like this instead:
/\r\n|\n|\r/g
Hope that helps.
you are missing the ending semicolons ; in your code:
string_convert = function(aString){
return aString.replace("↵",'<br>').replace('↵','<br>');
}
this does not necessary solve your problem, but it could likely.
From: Trying to translate a carriage return into a html tag in Javascript?
text = text.replace(/(\r\n|\n|\r)/g,"<br />");
I want to use JQ to print to a div on my page. The string I want to print with contains HTML including apostrophes and double apostrophes.
Is there a plugin or function to escape this so that the string doesnt break the js variable? There may be the case that I can't escape all of the apostrophes and double apostrophes in the incoming data using a backslash, so I'm looking for a function that can do it.
EG;
var replacement = 'This content has an apostrophe ' and a double apostrophe "';
$("#overwrite").text(replacement);
TIA
If you wanted to type out a string that is assigned to a variable like in your example above, then just escape it yourself.
For example, if I know my data will have apostrophes, then I wrap it in quotes (what you are calling double apostrophes) and use the HTML shortcut for quotes " or you can use a backslash to escape the quote \". Either way works. So your example above would become:
var replacement = "This content has an apostrophe ' and a double apostrophe "";
If the user is typing in the string or you are getting data from a feed, then it would be best to use the javascript replace function to make sure the quotes are escaped, like this:
var text = $("input").val().replace(/\"/g,""");
There is no need to escape incoming data, as it is already a string.
The only reason you need to escape apostrophes and double apostrophes in JavaScript source is due to the fact the JavaScript engine has to determine where the string starts and ends.
For instance, assuming you have a div#source containing the text "Hi there, what's up!", it is perfectly safe to do $("#overwrite").text($("#source").text()).
In Javascript, when I put a backslash in some variables like:
var ttt = "aa ///\\\";
var ttt = "aa ///\";
Javascript shows an error.
If I try to restrict user in entering this character, I also get an error:
(("aaa ///\\\").indexOf('"') != -1)
Restricting backslashes from user input is not a good strategy, because you have to show an annoying message to the user.
Why am I getting an error with backslash?
The backslash (\) is an escape character in Javascript (along with a lot of other C-like languages). This means that when Javascript encounters a backslash, it tries to escape the following character. For instance, \n is a newline character (rather than a backslash followed by the letter n).
In order to output a literal backslash, you need to escape it. That means \\ will output a single backslash (and \\\\ will output two, and so on). The reason "aa ///\" doesn't work is because the backslash escapes the " (which will print a literal quote), and thus your string is not properly terminated. Similarly, "aa ///\\\" won't work, because the last backslash again escapes the quote.
Just remember, for each backslash you want to output, you need to give Javascript two.
You may want to try the following, which is more or less the standard way to escape user input:
function stringEscape(s) {
return s ? s.replace(/\\/g,'\\\\').replace(/\n/g,'\\n').replace(/\t/g,'\\t').replace(/\v/g,'\\v').replace(/'/g,"\\'").replace(/"/g,'\\"').replace(/[\x00-\x1F\x80-\x9F]/g,hex) : s;
function hex(c) { var v = '0'+c.charCodeAt(0).toString(16); return '\\x'+v.substr(v.length-2); }
}
This replaces all backslashes with an escaped backslash, and then proceeds to escape other non-printable characters to their escaped form. It also escapes single and double quotes, so you can use the output as a string constructor even in eval (which is a bad idea by itself, considering that you are using user input). But in any case, it should do the job you want.
You have to escape each \ to be \\:
var ttt = "aa ///\\\\\\";
Updated: I think this question is not about the escape character in string at all. The asker doesn't seem to explain the problem correctly.
because you had to show a message to user that user can't give a name which has (\) character.
I think the scenario is like:
var user_input_name = document.getElementById('the_name').value;
Then the asker wants to check if user_input_name contains any [\]. If so, then alert the user.
If user enters [aa ///\] in HTML input box, then if you alert(user_input_name), you will see [aaa ///\]. You don't need to escape, i.e. replace [\] to be [\\] in JavaScript code. When you do escaping, that is because you are trying to make of a string which contain special characters in JavaScript source code. If you don't do it, it won't be parsed correct. Since you already get a string, you don't need to pass it into an escaping function. If you do so, I am guessing you are generating another JavaScript code from a JavaScript code, but it's not the case here.
I am guessing asker wants to simulate the input, so we can understand the problem. Unfortunately, asker doesn't understand JavaScript well. Therefore, a syntax error code being supplied to us:
var ttt = "aa ///\";
Hence, we assume the asker having problem with escaping.
If you want to simulate, you code must be valid at first place.
var ttt = "aa ///\\"; // <- This is correct
// var ttt = "aa ///\"; // <- This is not.
alert(ttt); // You will see [aa ///\] in dialog, which is what you expect, right?
Now, you only need to do is
var user_input_name = document.getElementById('the_name').value;
if (user_input_name.indexOf("\\") >= 0) { // There is a [\] in the string
alert("\\ is not allowed to be used!"); // User reads [\ is not allowed to be used]
do_something_else();
}
Edit: I used [] to quote text to be shown, so it would be less confused than using "".
The backslash \ is reserved for use as an escape character in Javascript.
To use a backslash literally you need to use two backslashes
\\
If you want to use special character in javascript variable value, Escape Character (\) is required.
Backslash in your example is special character, too.
So you should do something like this,
var ttt = "aa ///\\\\\\"; // --> ///\\\
or
var ttt = "aa ///\\"; // --> ///\
But Escape Character not require for user input.
When you press / in prompt box or input field then submit, that means single /.