function str_replace(search, replace, subject, count) {
  //  discuss at: http://phpjs.org/functions/str_replace/
  // original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // improved by: Gabriel Paderni
  // improved by: Philip Peterson
  // improved by: Simon Willison (http://simonwillison.net)
  // improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // improved by: Onno Marsman
  // improved by: Brett Zamir (http://brett-zamir.me)
  //  revised by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
  // bugfixed by: Anton Ongson
  // bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // bugfixed by: Oleg Eremeev
  //    input by: Onno Marsman
  //    input by: Brett Zamir (http://brett-zamir.me)
  //    input by: Oleg Eremeev
  //        note: The count parameter must be passed as a string in order
  //        note: to find a global variable in which the result will be given
  //   example 1: str_replace(' ', '.', 'Kevin van Zonneveld');
  //   returns 1: 'Kevin.van.Zonneveld'
  //   example 2: str_replace(['{name}', 'l'], ['hello', 'm'], '{name}, lars');
  //   returns 2: 'hemmo, mars'
  // bugfixed by: Glen Arason (http://CanadianDomainRegistry.ca)
  //   example 3: str_replace(Array('S','F'),'x','ASDFASDF');
  //   returns 3: 'AxDxAxDx'

  var i = 0,
    j = 0,
    temp = '',
    repl = '',
    sl = 0,
    fl = 0,
    f = [].concat(search),
    r = [].concat(replace),
    s = subject,
    ra = Object.prototype.toString.call(r) === '[object Array]',
    sa = Object.prototype.toString.call(s) === '[object Array]';
  s = [].concat(s);
  
  if(typeof(search) == 'object' && typeof(replace) == 'string' ) {
    temp = replace; replace = new Array();
    for (i=0; i < search.length; i+=1) { replace[i] = temp; }
    // update vars 
    temp = ''; r = [].concat(replace); ra = Object.prototype.toString.call(r) === '[object Array]';
  }
  
  if (count) {
    this.window[count] = 0;
  }

  for (i = 0, sl = s.length; i < sl; i++) {
    if (s[i] === '') {
      continue;
    }
    for (j = 0, fl = f.length; j < fl; j++) {
      temp = s[i] + '';
      repl = ra ? (r[j] !== undefined ? r[j] : '') : r[0];
      s[i] = (temp)
        .split(f[j])
        .join(repl);
      if (count && s[i] !== temp) {
        this.window[count] += (temp.length - s[i].length) / f[j].length;
      }
    }
  }
  return sa ? s : s[0];
}

function str_replace(search, replace, subject, count) {
  //  discuss at: http://phpjs.org/functions/str_replace/
  // original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // improved by: Gabriel Paderni
  // improved by: Philip Peterson
  // improved by: Simon Willison (http://simonwillison.net)
  // improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // improved by: Onno Marsman
  // improved by: Brett Zamir (http://brett-zamir.me)
  //  revised by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
  // bugfixed by: Anton Ongson
  // bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // bugfixed by: Oleg Eremeev
  //    input by: Onno Marsman
  //    input by: Brett Zamir (http://brett-zamir.me)
  //    input by: Oleg Eremeev
  //        note: The count parameter must be passed as a string in order
  //        note: to find a global variable in which the result will be given
  //   example 1: str_replace(' ', '.', 'Kevin van Zonneveld');
  //   returns 1: 'Kevin.van.Zonneveld'
  //   example 2: str_replace(['{name}', 'l'], ['hello', 'm'], '{name}, lars');
  //   returns 2: 'hemmo, mars'
  // bugfixed by: Glen Arason (http://CanadianDomainRegistry.ca)
  //   example 3: str_replace(Array('S','F'),'x','ASDFASDF');
  //   returns 3: 'AxDxAxDx'

  var i = 0,
    j = 0,
    temp = '',
    repl = '',
    sl = 0,
    fl = 0,
    f = [].concat(search),
    r = [].concat(replace),
    s = subject,
    ra = Object.prototype.toString.call(r) === '[object Array]',
    sa = Object.prototype.toString.call(s) === '[object Array]';
  s = [].concat(s);
  
  if(typeof(search) === 'object' && typeof(replace) === 'string' ) {
    temp = replace; 
    replace = new Array();
    for (i=0; i < search.length; i+=1) { 
      replace[i] = temp; 
    }
    temp = ''; 
    r = [].concat(replace); 
    ra = Object.prototype.toString.call(r) === '[object Array]';
  }
  
  if (count) {
    this.window[count] = 0;
  }

  for (i = 0, sl = s.length; i < sl; i++) {
    if (s[i] === '') {
      continue;
    }
    for (j = 0, fl = f.length; j < fl; j++) {
      temp = s[i] + '';
      repl = ra ? (r[j] !== undefined ? r[j] : '') : r[0];
      s[i] = (temp)
        .split(f[j])
        .join(repl);
      if (count && s[i] !== temp) {
        this.window[count] += (temp.length - s[i].length) / f[j].length;
      }
    }
  }
  return sa ? s : s[0];
}

Update str_replace.js