phpjs/functions/xml/utf8_encode.js

php.js offers community built php functions in javascript

function utf8_encode(argString) {
  //  discuss at: http://phpjs.org/functions/utf8_encode/
  // original by: Webtoolkit.info (http://www.webtoolkit.info/)
  // improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // improved by: sowberry
  // improved by: Jack
  // improved by: Yves Sucaet
  // improved by: kirilloid
  // bugfixed by: Onno Marsman
  // bugfixed by: Onno Marsman
  // bugfixed by: Ulrich
  // bugfixed by: Rafal Kukawski
  // bugfixed by: kirilloid
  //   example 1: utf8_encode('Kevin van Zonneveld');
  //   returns 1: 'Kevin van Zonneveld'

  if (argString === null || typeof argString === 'undefined') {
    return '';
  }

  var string = (argString + ''); // .replace(/\r\n/g, "\n").replace(/\r/g, "\n");
  var utftext = '',
    start, end, stringl = 0;

  start = end = 0;
  stringl = string.length;
  for (var n = 0; n < stringl; n++) {
    var c1 = string.charCodeAt(n);
    var enc = null;

    if (c1 < 128) {
      end++;
    } else if (c1 > 127 && c1 < 2048) {
      enc = String.fromCharCode(
        (c1 >> 6) | 192, (c1 & 63) | 128
      );
    } else if ((c1 & 0xF800) != 0xD800) {
      enc = String.fromCharCode(
        (c1 >> 12) | 224, ((c1 >> 6) & 63) | 128, (c1 & 63) | 128
      );
    } else { // surrogate pairs
      if ((c1 & 0xFC00) != 0xD800) {
        throw new RangeError('Unmatched trail surrogate at ' + n);
      }
      var c2 = string.charCodeAt(++n);
      if ((c2 & 0xFC00) != 0xDC00) {
        throw new RangeError('Unmatched lead surrogate at ' + (n - 1));
      }
      c1 = ((c1 & 0x3FF) << 10) + (c2 & 0x3FF) + 0x10000;
      enc = String.fromCharCode(
        (c1 >> 18) | 240, ((c1 >> 12) & 63) | 128, ((c1 >> 6) & 63) | 128, (c1 & 63) | 128
      );
    }
    if (enc !== null) {
      if (end > start) {
        utftext += string.slice(start, end);
      }
      utftext += enc;
      start = end = n + 1;
    }
  }

  if (end > start) {
    utftext += string.slice(start, stringl);
  }

  return utftext;
}