Develop Reference

I have to make a split function in JavaScript

Edit
sorry if the question wasn't clear
here is the question..
create your version of javascript split function,
you may use indexOf and substring to help.
so if i give you a string "heellloolllloolllo" and i want to remove "llll" the function should return "heellloooolllo"
This what I did so far:
function split() {
var entered_string = document.forms["form1"]["str"].value;
var deleted_char = document.forms["form1"]["char"].value;
var index = entered_string.indexOf(deleted_char);
var i = deleted_char.length;
var result;
var x ;
for (x = 0; x< entered_string.length; x++ )
{
if (index < 0) {
result = entered_string;
} else {
result = entered_string.substring(0, index) +entered_string.substring(index+i);
}
}
alert(result)
}

Use the replace() function with the g at the end of your regular expression. It's called a "global modifier".
var string = 'heellloolllloolllo';
var res = string.replace(/llll/g, '');
console.log(res)
If your substring is a variable then you need to construct a new Regex object and set the g as the second parameter.
var string = 'heellloolllloolllo';
var find = 'llll';
var regex = new RegExp(find,'g');
var res = string.replace(regex, '');
console.log(res)
There are other useful modifiers you can use:
g - Global replace. Replace all instances of the matched string in the provided text.
i - Case insensitive replace. Replace all instances of the matched string, ignoring differences in case.
m - Multi-line replace. The regular expression should be tested for matches over multiple lines.
See this post for more information, credit to #codejoe.

Using String#replace and RegExp (the clean way)
var str = 'llllheellloolllloolllollll';
var matchStr = 'llll';
function removeSubString(str, matchStr) {
var re = new RegExp(matchStr, 'g');
return str.replace(re,"");
}
console.log(removeSubString(str, matchStr));
Using String#indexOf and String#substring
var str = 'llllheellloolllloolllollll';
var matchStr = 'llll';
function removeSubString(str, matchStr) {
var index = str.indexOf(matchStr);
while(index != -1) {
var firstSubStr = str.substring(0, index);
var lastSubStr = str.substring(index + matchStr.length);
str = firstSubStr + lastSubStr;
index = str.indexOf(matchStr);
}
return str;
}
console.log(removeSubString(str,matchStr))

JavaScript replace string and comma if comma exists else only the string

I got a string like:
var string = "string1,string2,string3,string4";
I got to replace a given value from the string. So the string for example becomes like this:
var replaced = "string1,string3,string4"; // `string2,` is replaced from the string
Ive tried to do it like this:
var valueToReplace = "string2";
var replace = string.replace(',' + string2 + ',', '');
But then the output is:
string1string3,string4
Or if i have to replace string4 then the replace function doesn't replace anything, because the comma doens't exist.
How can i replace the value and the commas if the comma(s) exists?
If the comma doesn't exists, then only replace the string.

Modern browsers
var result = string.split(',').filter( s => s !== 'string2').join(',');
For older browsers
var result = string.split(',').filter( function(s){ return s !== 'string2'}).join(',');
First you split string into array such as ['string1', 'string2', 'string3', 'string4' ]
Then you filter out unwanted item with filter. So you are left with ['string1', 'string3', 'string4' ]
join(',') convertes your array into string using , separator.

Split the string by comma.
You get all Strings as an array and remove the item you want.
Join back them by comma.
var string = "string1,string2,string3,string4";
var valueToReplace = "string2";
var parts = string.split(",");
parts.splice(parts.indexOf(valueToReplace), 1);
var result = parts.join(",");
console.log(result);

You only need to replace one of the two commas not both, so :
var replace = string.replace(string2 + ',', '');
Or :
var replace = string.replace(',' + string2, '');
You can check for the comma by :
if (string.indexOf(',' + string2)>-1) {
var replace = string.replace(',' + string2, '');
else if (string.indexOf(string2 + ',', '')>-1) {
var replace = string.replace(string2 + ',', '');
} else { var replace = string.replace(string2,''); }

You should replace only 1 comma and also pass the correct variable to replace method such as
var string = "string1,string2,string3,string4";
var valueToReplace = "string2";
var replaced = string.replace(valueToReplace + ',', '');
alert(replaced);

You can replace the string and check after that for the comma
var replace = string.replace(string2, '');
if(replace[replace.length - 1] === ',')
{
replace = replace.slice(0, -1);
}

You can use string function replace();
eg:
var string = "string1,string2,string3,string4";
var valueToReplace = ",string2";
var replaced = string.replace(valueToReplace,'');
or if you wish to divide it in substring you can use substr() function;
var string = "string1,string2,string3,string4";
firstComma = string.indexOf(',')
var replaced = string.substr(0,string.indexOf(','));
secondComma = string.indexOf(',', firstComma + 1)
replaced += string.substr(secondComma , string.length);
you can adjust length as per your choice of comma by adding or subtracting 1.

str = "string1,string2,string3"
tmp = []
match = "string3"
str.split(',').forEach(e=>{
if(e != match)
tmp.push(e)
})
console.log(tmp.join(','))
okay i got you. here you go.

Your question is - How can i replace the value and the commas if the comma(s) exists?
So I'm assuming that string contains spaces also.
So question is - how can we detect the comma existence in string?
Simple, use below Javascript condition -
var string = "string1 string2, string3, string4";
var stringToReplace = "string2";
var result;
if (string.search(stringToReplace + "[\,]") === -1) {
result = string.replace(stringToReplace,'');
} else {
result = string.replace(stringToReplace + ',','');
}
document.getElementById("result").innerHTML = result;
<p id="result"></p>

How to get parameter value inside a string?

Here's a thing i've been trying to resolve...
We've got some data from an ajax call and the result data is between other stuff a huge string with key:value data. For example:
"2R=OK|2M=2 row(s) found|V1=1,2|"
Is it posible for js to do something like:
var value = someFunction(str, param);
so if i search for "V1" parameter it will return "1,2"
I got this running on Sql server no sweat, but i'm struggling with js to parse the string.
So far i'm able to do this by a VERY rudimentary for loop like this:
var str = "2R=OK|2M=2 row(s) found|V1=1,2|";
var param = "V1";
var arr = str.split("|");
var i = 0;
var value = "";
for(i = 0; i<arr.length; ++i){
if( arr[i].indexOf(param)>-1 ){
value = arr[i].split("=")[1];
}
}
console.log(value);
if i put that into a function it works, but i wonder if there's a more efficient way to do it, maybe some regex? but i suck at it. Hopefully somebody may shine a light on this for me?
Thanks!

This seems to work for your specific use-case:
function getValueByKey(haystack, needle) {
if (!haystack || !needle) {
return false;
}
else {
var re = new RegExp(needle + '=(.+)');
return haystack.match(re)[1];
}
}
var str = "2R=OK|2M=2 row(s) found|V1=1,2|",
test = getValueByKey(str, 'V1');
console.log(test);
JS Fiddle demo.
And, to include the separator in your search (in order to prevent somethingElseV1 matching for V1):
function getValueByKey(haystack, needle, separator) {
if (!haystack || !needle) {
return false;
}
else {
var re = new RegExp('\\' + separator + needle + '=(.+)\\' + separator);
return haystack.match(re)[1];
}
}
var str = "2R=OK|2M=2 row(s) found|V1=1,2|",
test = getValueByKey(str, 'V1', '|');
console.log(test);
JS Fiddle demo.
Note that this approach does require the use of the new RegExp() constructor (rather than creating a regex-literal using /.../) in order to pass variables into the regular expression.
Similarly, because we're using a string to create the regular expression within the constructor, we need to double-escape characters that require escaping (escaping first within the string and then escaping within in the created RegExp).
References:
RegExp.
String.match().

This should work for you and it's delimiters are configurable (if you wish to parse a similar string with different delimiters, you can just pass in the delimiters as arguments):
var parseKeyValue = (function(){
return function(str, search, keyDelim, valueDelim){
keyDelim = quote(keyDelim || '|');
valueDelim = quote(valueDelim || '=');
var regexp = new RegExp('(?:^|' + keyDelim + ')' + quote(search) + valueDelim + '(.*?)(?:' + keyDelim + '|$)');
var result = regexp.exec(str);
if(result && result.length > 1)
return result[1];
};
function quote(str){
return (str+'').replace(/([.?*+^$[\]\\(){}|-])/g, "\\$1");
}
})();
Quote function borrowed form this answer
Usage examples:
var str = "2R=OK|2M=2 row(s) found|V1=1,2|";
var param = "V1";
parseKeyValue(str, param); // "1,2"
var str = "2R=OK&2M=2 row(s) found&V1=1,2";
var param = "2R";
parseKeyValue(str, param, '&'); // "OK"
var str =
"2R=>OK\n\
2M->2 row(s) found\n\
V1->1,2";
var param = "2M";
parseKeyValue(str, param, '\n', '->'); // "2 row(s) found"

Here is another approach:
HTML:
<div id="2R"></div>
<div id="2M"></div>
<div id="V1"></div>
Javascript:
function createDictionary(input) {
var splittedInput = input.split(/[=|]/),
kvpCount = Math.floor(splittedInput.length / 2),
i, key, value,
dictionary = {};
for (i = 0; i < kvpCount; i += 1) {
key = splittedInput[i * 2];
value = splittedInput[i * 2 + 1];
dictionary[key] = value;
}
return dictionary;
}
var input = "2R=OK|2M=2 row(s) found|V1=1,2|",
dictionary = createDictionary(input),
div2R = document.getElementById("2R"),
div2M = document.getElementById("2M"),
divV1 = document.getElementById("V1");
div2R.innerHTML = dictionary["2R"];
div2M.innerHTML = dictionary["2M"];
divV1.innerHTML = dictionary["V1"];
Result:
OK
2 row(s) found
1,2

Create JSON object from a path and template

I'm a lazy coder by nature, so would like to know that there's a lib out there that does the following before I write on:
var parser = PathParser('/{first}/{last}');
var actual = parser.parse('/fred/flintstone');
assertEquals({"first":"fred","last":"flintstone"}, actual);
The first string specifies a pattern, and the second extracts the relevant values and stores them in an object with keys corresponding to those in the pattern.
I've found the standard that does the expansion, but not the generation of the JSON Object.

You want to extract an array of keys from your first string and extract an array of values from the latter, where the value is preceded by a certain pattern and followed by a certain pattern.
There isn't an existing library that does this, but I have written an implementation. You can find a live demonstration here.
//## Extension to escape all regex special characters in a string ##
RegExp.quote = function(str) {
return (str + '').replace(/([.?*+^$[\]\\(){}|-])/g, "\\$1");
};
//## Parsing ##
var parser = PathParser('/{first}/{last}');
var actual = parser('/fred/flintstone');
//## Output ##
var pre = document.createElement('pre');
pre.innerHTML = JSON.stringify(actual, null, " ");
document.body.appendChild(pre);
//## The parser constructor ##
function PathParser(pattern) {
var keys = [];
var keyreg = /\{([a-zA-Z0-9]+)\}/g;
var result;
while ((result = keyreg.exec(pattern)) !== null) {
var pre = "^" + RegExp.quote(pattern.substring(0, result.index)).replace(/\\\{[a-zA-Z0-9]+\\\}/g, ".*");
var post = RegExp.quote(pattern.substring(keyreg.lastIndex)).replace(/\\\{[a-zA-Z0-9]+\\\}/g, ".*") + "$";
keys.push({
pre: pre,
post: post,
text: result[1]
});
}
function parser(valstring) {
var keyarr = keys;
var obj = {};
for (var i = 0; i < keyarr.length; i++) {
var valreg = new RegExp(keyarr[i].pre + "(.*)" + keyarr[i].post);
obj[keyarr[i].text] = valstring.match(valreg)[1];
}
return obj;
}
return parser;
}

Remove all occurrences except last?

I want to remove all occurrences of substring = . in a string except the last one.
E.G:
1.2.3.4
should become:
123.4

You can use regex with positive look ahead,
"1.2.3.4".replace(/[.](?=.*[.])/g, "");

2-liner:
function removeAllButLast(string, token) {
/* Requires STRING not contain TOKEN */
var parts = string.split(token);
return parts.slice(0,-1).join('') + token + parts.slice(-1)
}
Alternative version without the requirement on the string argument:
function removeAllButLast(string, token) {
var parts = string.split(token);
if (parts[1]===undefined)
return string;
else
return parts.slice(0,-1).join('') + token + parts.slice(-1)
}
Demo:
> removeAllButLast('a.b.c.d', '.')
"abc.d"
The following one-liner is a regular expression that takes advantage of the fact that the * character is greedy, and that replace will leave the string alone if no match is found. It works by matching [longest string including dots][dot] and leaving [rest of string], and if a match is found it strips all '.'s from it:
'a.b.c.d'.replace(/(.*)\./, x => x.replace(/\./g,'')+'.')
(If your string contains newlines, you will have to use [.\n] rather than naked .s)

You can do something like this:
var str = '1.2.3.4';
var last = str.lastIndexOf('.');
var butLast = str.substring(0, last).replace(/\./g, '');
var res = butLast + str.substring(last);
Live example:
http://jsfiddle.net/qwjaW/

You could take a positive lookahead (for keeping the last dot, if any) and replace the first coming dots.
var string = '1.2.3.4';
console.log(string.replace(/\.(?=.*\.)/g, ''));

A replaceAllButLast function is more useful than a removeAllButLast function. When you want to remove just replace with an empty string:
function replaceAllButLast(str, pOld, pNew) {
var parts = str.split(pOld)
if (parts.length === 1) return str
return parts.slice(0, -1).join(pNew) + pOld + parts.slice(-1)
}
var test = 'hello there hello there hello there'
test = replaceAllButLast(test, ' there', '')
console.log(test) // hello hello hello there

Found a much better way of doing this. Here is replaceAllButLast and appendAllButLast as they should be done. The latter does a replace whilst preserving the original match. To remove, just replace with an empty string.
var str = "hello there hello there hello there"
function replaceAllButLast(str, regex, replace) {
var reg = new RegExp(regex, 'g')
return str.replace(reg, function(match, offset, str) {
var follow = str.slice(offset);
var isLast = follow.match(reg).length == 1;
return (isLast) ? match : replace
})
}
function appendAllButLast(str, regex, append) {
var reg = new RegExp(regex, 'g')
return str.replace(reg, function(match, offset, str) {
var follow = str.slice(offset);
var isLast = follow.match(reg).length == 1;
return (isLast) ? match : match + append
})
}
var replaced = replaceAllButLast(str, / there/, ' world')
console.log(replaced)
var appended = appendAllButLast(str, / there/, ' fred')
console.log(appended)
Thanks to #leaf for these masterpieces which he gave here.

You could reverse the string, remove all occurrences of substring except the first, and reverse it again to get what you want.

function formatString() {
var arr = ('1.2.3.4').split('.');
var arrLen = arr.length-1;
var outputString = '.' + arr[arrLen];
for (var i=arr.length-2; i >= 0; i--) {
outputString = arr[i]+outputString;
}
alert(outputString);
}
See it in action here: http://jsbin.com/izebay

var s='1.2.3.4';
s=s.split('.');
s.splice(s.length-1,0,'.');
s.join('');
123.4