String.prototype.replaceAll = function(character,replaceChar){
    var word = this.valueOf();

    while(word.indexOf(character) != -1)
        word = word.replace(character,replaceChar);

    return word;
}

这更简洁/可读，应该比Fagner Brack发布的更好(toLowerCase不是在循环中执行的):

String.prototype.replaceAll = function(search, replace, ignoreCase) {
  if (ignoreCase) {
    var result = [];
    var _string = this.toLowerCase();
    var _search = search.toLowerCase();
    var start = 0, match, length = _search.length;
    while ((match = _string.indexOf(_search, start)) >= 0) {
      result.push(this.slice(start, match));
      start = match + length;
    }
    result.push(this.slice(start));
  } else {
    result = this.split(search);
  }
  return result.join(replace);
}

用法:

alert('Bananas And Bran'.replaceAll('An', '(an)'));

对于这个简单的场景，我也建议使用javascript内置的方法。

你可以试试这个:

"okay.this.is.a.string".split(".").join("")

问候

@scripto变得更简洁，没有原型:

function strReplaceAll(s, stringToFind, stringToReplace) {
    if (stringToFind === stringToReplace) return s;
    for (let index = s.indexOf(stringToFind); index != -1; index = s.indexOf(stringToFind))
        s = s.replace(stringToFind, stringToReplace);
    return s;
}

以下是它的累积情况:http://jsperf.com/replace-vs-split-join-vs-replaceall/68

简单的方法

“先生”.split (' . ') . join (" ");

..............

控制台

我加了双反斜杠的点，使它工作。欢呼。

var st = "okay.this.is.a.string";
var Re = new RegExp("\\.","g");
st = st.replace(Re," ");
alert(st);