es6.regexp.split.js

// @@split logic
require('./_fix-re-wks')('split', 2, function(defined, SPLIT, $split){
  'use strict';
  var isRegExp   = require('./_is-regexp')
    , _split     = $split
    , $push      = [].push
    , $SPLIT     = 'split'
    , LENGTH     = 'length'
    , LAST_INDEX = 'lastIndex';
  if(
    'abbc'[$SPLIT](/(b)*/)[1] == 'c' ||
    'test'[$SPLIT](/(?:)/, -1)[LENGTH] != 4 ||
    'ab'[$SPLIT](/(?:ab)*/)[LENGTH] != 2 ||
    '.'[$SPLIT](/(.?)(.?)/)[LENGTH] != 4 ||
    '.'[$SPLIT](/()()/)[LENGTH] > 1 ||
    ''[$SPLIT](/.?/)[LENGTH]
  ){
    var NPCG = /()??/.exec('')[1] === undefined; // nonparticipating capturing group
    // based on es5-shim implementation, need to rework it
    $split = function(separator, limit){
      var string = String(this);
      if(separator === undefined && limit === 0)return [];
      // If `separator` is not a regex, use native split
      if(!isRegExp(separator))return _split.call(string, separator, limit);
      var output = [];
      var flags = (separator.ignoreCase ? 'i' : '') +
                  (separator.multiline ? 'm' : '') +
                  (separator.unicode ? 'u' : '') +
                  (separator.sticky ? 'y' : '');
      var lastLastIndex = 0;
      var splitLimit = limit === undefined ? 4294967295 : limit >>> 0;
      // Make `global` and avoid `lastIndex` issues by working with a copy
      var separatorCopy = new RegExp(separator.source, flags + 'g');
      var separator2, match, lastIndex, lastLength, i;
      // Doesn't need flags gy, but they don't hurt
      if(!NPCG)separator2 = new RegExp('^' + separatorCopy.source + '$(?!\\s)', flags);
      while(match = separatorCopy.exec(string)){
        // `separatorCopy.lastIndex` is not reliable cross-browser
        lastIndex = match.index + match[0][LENGTH];
        if(lastIndex > lastLastIndex){
          output.push(string.slice(lastLastIndex, match.index));
          // Fix browsers whose `exec` methods don't consistently return `undefined` for NPCG
          if(!NPCG && match[LENGTH] > 1)match[0].replace(separator2, function(){
            for(i = 1; i < arguments[LENGTH] - 2; i++)if(arguments[i] === undefined)match[i] = undefined;
          });
          if(match[LENGTH] > 1 && match.index < string[LENGTH])$push.apply(output, match.slice(1));
          lastLength = match[0][LENGTH];
          lastLastIndex = lastIndex;
          if(output[LENGTH] >= splitLimit)break;
        }
        if(separatorCopy[LAST_INDEX] === match.index)separatorCopy[LAST_INDEX]++; // Avoid an infinite loop
      }
      if(lastLastIndex === string[LENGTH]){
        if(lastLength || !separatorCopy.test(''))output.push('');
      } else output.push(string.slice(lastLastIndex));
      return output[LENGTH] > splitLimit ? output.slice(0, splitLimit) : output;
    };
  // Chakra, V8
  } else if('0'[$SPLIT](undefined, 0)[LENGTH]){
    $split = function(separator, limit){
      return separator === undefined && limit === 0 ? [] : _split.call(this, separator, limit);
    };
  }
  // 21.1.3.17 String.prototype.split(separator, limit)
  return [function split(separator, limit){
    var O  = defined(this)
      , fn = separator == undefined ? undefined : separator[SPLIT];
    return fn !== undefined ? fn.call(separator, O, limit) : $split.call(String(O), separator, limit);
  }, $split];
});