Develop Reference

Javascript remove double quotes from string having forward slash

What I have : I have following string "/.\*n.*/"
What I want : I want to remove double quotes from above string which will look like /.\*n.*/
What I tried :
var filter = "/.\*n.*/";
var modifiedFilter = filter.replace(/"/g, "");
Somehow this code is not working. When I look at modifiedFilter in debug mode, It still shows string with double quotes "/.\*n.*/".
Is it because its a string variable and debug value shows string in double quotes?
But if it is the case, then I am passing this variable to mongodb query and there query is not working due to double quotes.
What am I missing?

// To have quotes in your string, assign it like following:
var filter = '"/.\*n.*/"';
// Your code to remove the quotes is correct.
var modifiedFilter = filter.replace(/"/g, "");
// Verify that the code worked
console.log(filter, modifiedFilter)

It is impossible to remove " from "/.\*n.*/"; in your case as it is required to create strings. It is only possible if "/.\*n.*/"; denotes the actual value of the string and in that case assignment should look like var filter = '"/.\*n.*/"', and this problem will have sense for the answerers.
Just use var modifiedFilter = filter.replace(/\"/g, "").
First have a look at the below statements executed on Node REPL.
> s = "/.\*n.*/"
'/.*n.*/'
>
> s.replace(/'/g, '')
'/.*n.*/'
>
> s = "'/.\*n.*/'"
'\'/.*n.*/\''
>
> s.replace(/'/g, '')
'/.*n.*/'
>
Now have a look at the below code.
var s = '"/.\*n.*/"'
var output = s.replace(/\"/g, "")
console.log(s) // "/.*n.*/"
console.log(output) // /.*n.*/

Your problem here is either with the query, or with attempting to treat a string primitive directly as a regular expression. Instead of trying to remove the (non-existent) speech marks, instead use the RegExp constructor to convert it into a regular expression.
var filter = "/.\*n.*/";
var modifiedFilter = new RegExp(filter).slice(1, -1);
The string needs to be sliced because the RegExp constructor accepts a regular expression without // marks.

Extract Twitter handlers from string using regex in JavaScript

I Would like to extract the Twitter handler names from a text string, using a regex. I believe I am almost there, except for the ">" that I am including in my output. How can I change my regex to be better, and drop the ">" from my output?
Here is an example of a text string value:
"PlaymakersZA, Absa, DiepslootMTB"
The desired output would be an array consisting of the following:
PlaymakersZA, Absa, DiepslootMTB
Here is an example of my regex:
var array = str.match(/>[a-z-_]+/ig)
Thank you!

You can use match groups in your regex to indicate the part you wish to extract.
I set up this JSFiddle to demonstrate.
Basically, you surround the part of the regex that you want to extract in parenthesis: />([a-z-_]+)/ig, save it as an object, and execute .exec() as long as there are still values. Using index 1 from the resulting array, you can find the first match group's result. Index 0 is the whole regex, and next indices would be subsequent match groups, if available.
var str = "PlaymakersZA, Absa, DiepslootMTB";
var regex = />([a-z-_]+)/ig
var array = regex.exec(str);
while (array != null) {
alert(array[1]);
array = regex.exec(str);
}

You could just strip all the HTML
var str = "PlaymakersZA, Absa, DiepslootMTB";
$handlers = str.replace(/<[^>]*>|\s/g,'').split(",");

How to ignore escape characters in javascript?

I have the following string:
var str = '\x27';
I have no control on it, so I cannot write it as '\\x27' for example. Whenever I print it, i get:
'
since 27 is the apostrophe. When I call .length on it, it gives me 1. This is of course correct, but how can I treat it like a not escaped string and have it print literally
\x27
and give me a length of 4?

I'm not sure if you should do what you are trying to do, but this is how it works:
var s = '\x27';
var sEncoded = '\\x' + s.charCodeAt(0).toString(16);
s is a string that contains one character, the apostrophe. The character code as a hexadecimal number is 27.

After the assignment var str = '\x27';, you can't tell where the contents of str came from. There's no way to find out whether a string literal was assigned, or whether the string literal contained an escape sequence. All you have is a string containing a single apostrophe character (Unicode code point U+0027). The original assignment could have been
var str = '\x27'; // or
var str = "'"; // or
var str = String.fromCodePoint(3 * 13);
There's simply no way to tell.
That said, your question looks like an XY problem. Why are you trying to print \x27 in the first place?

Using regex to split double hyphen but not single hyphen

I have an html element id that looks like this:
dp__1-2--1-3
I'm trying to use the JavaScript split() function to lop off and return the final '1-3'
My regex skills are poor but a bit of searching around got me to this point:
var myId = "dp__1-2--1-3";
var myIdPostFix = myId.split(/[\-\-]+/).pop();
Unfortunately that returns me only the '3'.
So my question is how do I split double hyphens but NOT single hyphens?

It's the brackets in the regular expression that keeps it from working. A set will match one of any of the characers in it, so [\-\-] is the same as [\-], i.e. matching a single hyphen.
Just remove the brackets:
var myIdPostFix = myId.split(/--/).pop();
or just use the string '--' instead of a regular expression:
var myIdPostFix = myId.split('--').pop();

split accepts a regular expression or a string as the first argument.
You were very close. You can achieve what you want with:
var myIdPostFix = myId.split("--").pop();

javascript spilt to get part of the word

I tried use javascript spilt to get part of the word : new from What#a_new%20day
I tried code like this:
<script>
var word="What#a_new%20day";
var newword = word.split("%20", 1).split("_", 2);
alert(newword);
</script>
But caused:
Uncaught TypeError: Object What#a_new has no method 'split'
Maybe there have more wiser way to get the word which I need. So can anyone help me? Thanks.

split returns an array, so the second split is trying to operate on the array returned by the first, rather than a string, which causes a TypeError. You'll also want to add the correct index after the second call to split, or newword will also be an array, not the String you're expecting. Change it to:
var newword = word.split("%20", 1)[0].split("_", 2)[1];
This splits word, then splits the string at index 0 of the resulting array, and assigns the value of the string at index 1 of the new array to newword.

Regex to the rescue
var word="What#a_new%20day";
var newword = word.match(/_(.+)%/)[1];
alert(newword);
this returns the first ([1]) captured group ((...)) in the regex (_(.+)%) which is _ followed by any character (.) one or more times (+) followed by %.

the result of a split is an array, not a string. so what you need to do is
<script>
var word="What#a_new%20day";
var newword = word.split("%20", 1)[0].split("_", 2);
alert(newword);
</script>
notice the [0]

split returns an array:
https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/String/split
word.split("%20", 1);
gives an array so you cannot do :
(result from above).split("_", 2);

If split is what your after, go for it, but performance wise, it would be better to do something like this:
var word="What#a_new%20day";
var newword = word.substr(word.indexOf('new'),3)
alert(newword);
Live example: http://jsfiddle.net/qJ8wM/
Split searches for all instances of %20 in the text, whereas indexOf finds the first instance, and substr is fairly cheap performance wise as well.
JsPerf stats on split vs substring (a general case): http://jsperf.com/split-vs-substring