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remove second comma from a string in javascript

I have an string as:
0123456789,, 0987654213 ,, 0987334213,, ......
How can I convert this into
0123456789, 0987654213, 0987334213, ......
i.e I want to remove the second comma

You can do it very simply, like this using regex.
var str = "0123456789,,0987654213,,0987334213,,,,,9874578";
str=str.replace(/,*,/g,',');
console.log(str)

var str = "0123456789,, 0987654213 ,, 0987334213,, ......"
console.log(str.replace(/\,+/g,","));

This will replace all occurrences of consecutive commas with a single comma:
str.replace(/,+/g, ',');

You can use replace() method with regular expression with g flag to replace all instances ',,' with ',':
str.replace(/,,/g, ",");
Here's a simple example
var str = '0123456789,, 0987654213 ,, 0987334213';
str = str.replace(/,,/g, ",");
console.log(str);

var str = "0123456789,, 0987654213 ,, 0987334213,,"
str = str.split(",,").join(",")
console.log(str);

There is a replace method for String.
You can replace ',,' with a ','.
An example:
var str = "0123456789,, 0987654213,, 0987334213,";
var newStr = str.replace(/,,/g,','));
The output:
0123456789, 0987654213, 0987334213,

Add to current string using javascript

I would like to add to the current string using javascript. Currently, It is working fine but I am doing it in a very dirty way currently. I am basically replacing the WHOLE string instead of just adding to it. Is there a way that I can just add a comma and continue my string?
JS:
var mystring = "'bootstrap'"
console.log(mystring.replace(/bootstrap/g , "'bootstrap', 'bootstrap2', 'bootstrap3'"));
JSFiddle

You can add to the end of a string by using the +=operator. See the docs regarding string operators.
var mystring = "'bootstrap'"
mystring += ", 'bootstrap2'";
mystring += ", 'bootstrap3'";
console.log(mystring);

You can concatenate( + operator ) instead of replace if you just want the second string to get appended to the first string.
var mystring = "'bootstrap'"
var newString = mystring +", "+ "'bootstrap', 'bootstrap2', 'bootstrap3'";
console.log( newString );

What about:
mystring += "'bootstrap2',";
or
var arr = ["str1", "str2", "str3"];
var mystring = arr.map((e)=>{return "'"+e+"'";}).join(",")
Array.map function used to wrap each string with single quates, than you Array.join - used to put "," between members

You can concat strings with the + operator:
var mystring = "'bootstrap'" + ",";
console.log(mystring);

Use an array and the join method.
var arr = [];
var myString = "bootstrap";
arr.push(myString);
arr.push(myString);
arr.push("other string");
arr.push("bootstrap");
// combine them with a comma or something else
console.log(arr.join(', '));

It is not suggested, but if you want to keep symbols and not care about order, and want to only add to a string beginning with 'bootstrap':
myString = "'bootstrap'";
console.log(myString.replace(/^(?='(bootstrap)')/, "'$12', '$13', "));
or you can just use capture group to keep it short
mystring.replace(/'(bootstrap)'/, "'$1', '$12', '$13'")

Pattern match to get string between brackets

I am trying to find whatever string is in between the aggregate() and find(). Below is my code.
var str1 = 'aggregate([{$group:{_id:{state:"$state",city:"$city"},sum:{$sum:"$pop"}}},{$sort:{sum:1}},{$group:{_id:"$_id.state",smallestcity:{$first:"$_id.city"},smallest:{$first:"$sum"},largestcity:{$last:"$_id.city"},largest:{$last:"$sum"}}}])'
var str2 = 'find({awards:{$elemMatch:{award:"Turing Award",year:{$gt:1980}}}}).limit(0)'
var matchPharse = /((.*))/;
var result = str1.match(matchPharse);
console.log(result);
I am getting the result always the whole string instead of
[{$group:{_id:{state:"$state",city:"$city"},sum:{$sum:"$pop"}}},{$sort:{sum:1}},{$group:{_id:"$_id.state",smallestcity:{$first:"$_id.city"},smallest:{$first:"$sum"},largestcity:{$last:"$_id.city"},largest:{$last:"$sum"}}}]
I am searching for something like this

try this pattern instead:
var matchPharse = /((\[.*\]))/;

((\[.*?\]))
You Should use a non greedy expression.

Try the following RegEx:
var matchPharse= /\((.*)\)/g;
Matches any sequence between ().
This is a DEMO.
var str1 = 'aggregate([{$group:{_id:{state:"$state",city:"$city"},sum:{$sum:"$pop"}}},{$sort:{sum:1}},{$group:{_id:"$_id.state",smallestcity:{$first:"$_id.city"},smallest:{$first:"$sum"},largestcity:{$last:"$_id.city"},largest:{$last:"$sum"}}}])'
var str2 = 'find({awards:{$elemMatch:{award:"Turing Award",year:{$gt:1980}}}}).limit(0)'
var matchPharse = /\((.*)\)/;
var result = str1.match(matchPharse);
alert(result);

You just need to escape the outside parentheses. Try:
var matchPharse = /\((.*)\)/;
For just the content inside the parentheses use result[1]

jQuery string split the string after the space using split() method

my code
var str =$(this).attr('id');
this will give me value == myid 5
var str1 = myid
var str2 = 5
i want something like this ..
how to achieve this using split method

var str =$(this).attr('id');
var ret = str.split(" ");
var str1 = ret[0];
var str2 = ret[1];

Use in-built function: split()
var source = 'myid 5';
//reduce multiple places to single space and then split
var splittedSource = source.replace(/\s{2,}/g, ' ').split(' ');
console.log(splittedSource);
​
Note: this works even there is multiple spaces between the string groups
Fiddle: http://jsfiddle.net/QNSyr/6/

One line solution:
//<div id="mypost-5">
var postId = this.id.split('mypost-')[1] ); //better solution than the below one!
-OR-
//<div id="mypost-5">
var postId = $(this).attr('id').split('mypost-')[1];

Replace comma by double quote in javascript

How to replace comma by double quote in javascript?
For example: "c,C#,JavaScript" should be like "C","C#","JavaScript"

str = '"c,C#,JavaScript"';
str = str.split(',').join('","');
That would result in "c","C#","JavaScript"

var original = '"c,C#,JavaScript"';
var quoted = original.replace(/,/g, '","'); // "c","C#","JavaScript"

Just to toss it in there, you could also .split() and .join(), like this:
var oldString = '"c,C#,JavaScript"';
var newString = oldString.split(',').join('","');
You can test it here.

You can do this:
str = "c,C#,JavaScript";
str = str.replace(/,/g, '"');
Result:
c"C#"JavaScript