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Search in string and quote around occurrence

Working with Javascript I need to be able to search a string input from a user and replace occurrences of semicolons with commas. Issue I have ran into is I need to be able to search the string for any commas that already exist, and quote around to the last and next occurrence of the semicolon.
Example:
User input is 12345;Joran,Michael;02;17;63 it should be converted to 12345,"Joran,Michael",02,17,63
My includes is able to locate the occurrence of a comma in the original string var srch = source.includes(","); and my replace is var converted = source.replace(/;/g, ","); which works fine, just need to figure out how to get to the last/next semicolon to place the quotes.
Using an if/else depending on if srch evaluates to True -- if true, add the quotes and then convert the rest of the string and return to the user; if false, convert and return.
I'm sure there's a way to do this with regex that just hasn't came to me yet so any suggestions on what to look at would be great.

I'd do this in two steps. First match non-; characters which have at least one ,, and surround them with quotes. Then replace all ;s in the result with ,:
console.log(
'12345;Joran,Michael;02;17;63'
.replace(/[^;,]*,[^;]*/g, '"$&"')
.replace(/;/g, ',')
);

Split the string by ;
.split(';')
which gives you an array.
Convert the elements that include a ',' to "${element}"
.map(s => s.includes(',') ? `"${s}"` : s )
Convert the array back to string
.join(',')

var str = '12345;Joran,Michael;02;17;63';
var arr = str.split(";");
var letters = /^[A-Za-z]/;
var final_str = "";
for (var i = 0; i < arr.length; i++) {
final_str = arr[i].match(letters)?final_str +'"'+ arr[i]+'"'+",":final_str + arr[i]+",";
}
console.log(final_str.substring(0,final_str.length -1));

Javascript: String of text to array of characters

I'm trying to change a huge string into the array of chars. In other languages there is .toCharArray(). I've used split to take dots, commas an spaces from the string and make string array, but I get only separated words and don't know how to make from them a char array. or how to add another regular expression to separate word? my main goal is something else, but I need this one first. thanks
var str = " If you don't pass anything, you'll get an array containing only the original string, rather than an array containing each character."
str = str.toLowerCase();
str = str.split(/[ ,.]+/);

You can use String#replace with regex and String#split.
arrChar = str.replace(/[', ]/g,"").split('');
Demo:
var str = " If you don't pass anything, you'll get an array containing only the original string, rather than an array containing each character.";
var arrChar = str.replace(/[', ]/g,"").split('');
document.body.innerHTML = '<pre>' + JSON.stringify(arrChar, 0, 4) + '</pre>';
Add character in [] which you want to remove from string.

This will do:
var strAr = str.replace(/ /g,' ').toLowerCase().split("")

First you have to replace the , and . then you can split it:
var str = " If you don't pass anything, you'll get an array containing only the original string, rather than an array containing each character."
var strarr = str.replace(/[\s,.]+/g, "").split("");
document.querySelector('pre').innerHTML = JSON.stringify(strarr, 0, 4)
<pre></pre>

var charArray[];
for(var i = 0; i < str.length; i++) {
charArray.push(str.charAt(i));
}
Alternatively, you can simply use:
var charArray = str.split("");

I'm trying to change a huge string into the array of chars.
This will do
str = str.toLowerCase().split("");

The split() method is used to split a string into an array of
substrings, and returns the new array.
Tip: If an empty string ("") is used as the separator, the string is
split between each character.
Note: The split() method does not change the original string.
Please read the link:
http://www.w3schools.com/jsref/jsref_split.asp

You may do it like this
var coolString,
charArray,
charArrayWithoutSpecials,
output;
coolString = "If you don't pass anything, you'll get an array containing only the original string, rather than an array containing each character.";
// does the magic, uses string as an array to slice
charArray = Array.prototype.slice.call(coolString);
// let's do this w/o specials
charArrayWithoutSpecials = Array.prototype.slice.call(coolString.replace(/[', ]/g,""))
// printing it here
output = "<b>With special chars:</b> " + JSON.stringify(charArray);
output += "<br/><br/>";
output += "<b>With special chars:</b> " + JSON.stringify(charArrayWithoutSpecials)
document.write(output);
another way would be
[].slice.call(coolString)

I guess this is what you are looking for. Ignoring all symbols and spaces and adding all characters in to an array with lower case.
var str = " If you don't pass anything, you'll get an array containing only the original string, rather than an array containing each character."
str = str.replace(/\W/g, '').toLowerCase().split("");
alert(str);

Remove (n)th space from string in JavaScript

I am trying to remove some spaces from a few dynamically generated strings. Which space I remove depends on the length of the string. The strings change all the time so in order to know how many spaces there are, I iterate over the string and increment a variable every time the iteration encounters a space. I can already remove all of a specific type of character with str.replace(' ',''); where 'str' is the name of my string, but I only need to remove a specific occurrence of a space, not all the spaces. So let's say my string is
var str = "Hello, this is a test.";
How can I remove ONLY the space after the word "is"? (Assuming that the next string will be different so I can't just write str.replace('is ','is'); because the word "is" might not be in the next string).
I checked documentation on .replace, but there are no other parameters that it accepts so I can't tell it just to replace the nth instance of a space.

If you want to go by indexes of the spaces:
var str = 'Hello, this is a test.';
function replace(str, indexes){
return str.split(' ').reduce(function(prev, curr, i){
var separator = ~indexes.indexOf(i) ? '' : ' ';
return prev + separator + curr;
});
}
console.log(replace(str, [2,3]));
http://jsfiddle.net/96Lvpcew/1/

As it is easy for you to get the index of the space (as you are iterating over the string) , you can create a new string without the space by doing:
str = str.substr(0, index)+ str.substr(index);
where index is the index of the space you want to remove.

I came up with this for unknown indices
function removeNthSpace(str, n) {
var spacelessArray = str.split(' ');
return spacelessArray
.slice(0, n - 1) // left prefix part may be '', saves spaces
.concat([spacelessArray.slice(n - 1, n + 1).join('')]) // middle part: the one without the space
.concat(spacelessArray.slice(n + 1)).join(' '); // right part, saves spaces
}

Do you know which space you want to remove because of word count or chars count?
If char count, you can Rafaels Cardoso's answer,
If word count you can split them with space and join however you want:
var wordArray = str.split(" ");
var newStr = "";
wordIndex = 3; // or whatever you want
for (i; i<wordArray.length; i++) {
newStr+=wordArray[i];
if (i!=wordIndex) {
newStr+=' ';
}
}

I think your best bet is to split the string into an array based on placement of spaces in the string, splice off the space you don't want, and rejoin the array into a string.
Check this out:
var x = "Hello, this is a test.";
var n = 3; // we want to remove the third space
var arr = x.split(/([ ])/); // copy to an array based on space placement
// arr: ["Hello,"," ","this"," ","is"," ","a"," ","test."]
arr.splice(n*2-1,1); // Remove the third space
x = arr.join("");
alert(x); // "Hello, this isa test."
Further Notes
The first thing to note is that str.replace(' ',''); will actually only replace the first instance of a space character. String.replace() also accepts a regular expression as the first parameter, which you'll want to use for more complex replacements.
To actually replace all spaces in the string, you could do str.replace(/ /g,""); and to replace all whitespace (including spaces, tabs, and newlines), you could do str.replace(/\s/g,"");
To fiddle around with different regular expressions and see what they mean, I recommend using http://www.regexr.com
A lot of the functions on the JavaScript String object that seem to take strings as parameters can also take regular expressions, including .split() and .search().

Replace double commas until there are some

I am trying to replace all double commas with ,null,
The problem is that i need to keep doing it while it is replacing it. I am thinking about adding a loop but is there any other more eficient alternative?
var test = "[1,2,,,3,4,,,,,,5,6]".replace(/,{2}/g, ",null,");
alert(test);
The result should be:
"[1,2,null,null,3,4,null,null,null,null,null,5,6]"
But is instead:
[1,2,null,,3,4,null,,null,,null,5,6]
So I would have to create a loop and do it until all double commas are done. Not sure if there is any other way?
As a side info, this is so that I can afterwards do:
var myArray = $.parseJSON(test);
Which currently it fails which I'm guessing that it's because it is not valid json.

Single regex:
"[AB,,,CD,,,,,,EF]".replace(/,(?=,)/g, ',null');
demo
Here we use the ?= lookahead to find 2 commas ("comma with a comma after it") but match and replace only the first.
Edit:
You seem to be interested in speed, here are some tests.

str.split(',').map(function(x) { return x ? x : 'null' }).join(',');
FIDDLE
splits the string by commas, then map() iterates and returns each value from the callback, and the ternary returns x (the value) if thruthy and the string 'null' if falsy, which an empty string is, then join it back together again.

You can do this:
var test = "[1,2,,,3,4,,,,,,5,6]".split(',').join(',|').replace(/\|,/g,"null,");
alert(test.replace(/\|/g,""));
It alerts:
[1,2,null,null,3,4,null,null,null,null,null,5,6]
Demo: http://jsfiddle.net/AmitJoki/Zuv38/

Not sure if regex could handle that without looping.
Alternative solution is to split is into an array: '1,2,,,3,4,,,,,,5,6'.split(','); and then loop through it and replace all empty strings with null and then join it back.
So, something like this:
var s = '1,2,,,3,4,,,,,,5,6';
var a = s.split(',');
for (var i = 0; i < a.length; i++) {
if (a[i] == "") {
a[i] = "null";
}
}
s = '[' + a.join(',') + ']';
See it here: http://jsfiddle.net/fVMLv/1/

Try this
var str = "1,2,,,3,4,,,,,,5,6";
str = str.split(',');
var strResult ='';
$(str).each(function(){
if(this==''){
strResult +='null,';
}
else{
strResult +=this+',';
}
});
strResult = strResult.substring(0,strResult.length-1);
alert(strResult);
DEMO

The problem is with the double commas occurring consecutively.
,,,, -> will be taken as 2 sets of double commas by that RegExp. So, result will be:-
,null,,null, -> note that the occurrence of another double comma in between is skipped, since the RegEx is greedy (2nd comma is already used, which is not used again together with 3rd comma. rather 3rd and 4th are used together).
var test = "[AB,,,CD,,,,,,EF]".replace(/,,/g, ",null,").replace(/,,/g, ",null,");
alert(test);
So, with this RegExp, calling it twice will fix this.

How to match space separated strings?

but not an empty string?
// loop through space separated "tokens" in a string
// will loop through "" - needs update
$P.eachString = function (str, func, con) {
var regexp = /^|\s+/;
if (regexp.test(str)) {
// ... stuff
}
};
The code above will match "" the empty string. I want to match against
case1
some_string
case2
some_string1 some_string2
case3
some_string1 some_string2 some_string_3
etc.

Just use String.split and iterate over the returned array:
Splits a String object into an array of strings by separating the string into substrings.
If separator is omitted, the array contains one element consisting of the entire string.