Remove all occurrences except last?

Question

I want to remove all occurrences of substring = . in a string except the last one.

E.G:

1.2.3.4

should become:

Answer 1

var s='1.2.3.4';

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

123.4

Answer 2

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.

Answer 3

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

Answer 4

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, ''));

Answer 5

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)

Answer 6

You can use regex with positive look ahead,

"1.2.3.4".replace(/[.](?=.*[.])/g, "");