es.string.split.js

'use strict';
var fixRegExpWellKnownSymbolLogic = require('../internals/fix-regexp-well-known-symbol-logic');
var isRegExp = require('../internals/is-regexp');
var anObject = require('../internals/an-object');
var requireObjectCoercible = require('../internals/require-object-coercible');
var speciesConstructor = require('../internals/species-constructor');
var advanceStringIndex = require('../internals/advance-string-index');
var toLength = require('../internals/to-length');
var callRegExpExec = require('../internals/regexp-exec-abstract');
var regexpExec = require('../internals/regexp-exec');
var fails = require('../internals/fails');

var arrayPush = [].push;
var min = Math.min;
var MAX_UINT32 = 0xFFFFFFFF;

// babel-minify transpiles RegExp('x', 'y') -> /x/y and it causes SyntaxError
var SUPPORTS_Y = !fails(function () { return !RegExp(MAX_UINT32, 'y'); });

// @@split logic
fixRegExpWellKnownSymbolLogic('split', 2, function (SPLIT, nativeSplit, maybeCallNative) {
  var internalSplit;
  if (
    'abbc'.split(/(b)*/)[1] == 'c' ||
    'test'.split(/(?:)/, -1).length != 4 ||
    'ab'.split(/(?:ab)*/).length != 2 ||
    '.'.split(/(.?)(.?)/).length != 4 ||
    '.'.split(/()()/).length > 1 ||
    ''.split(/.?/).length
  ) {
    // based on es5-shim implementation, need to rework it
    internalSplit = function (separator, limit) {
      var string = String(requireObjectCoercible(this));
      var lim = limit === undefined ? MAX_UINT32 : limit >>> 0;
      if (lim === 0) return [];
      if (separator === undefined) return [string];
      // If `separator` is not a regex, use native split
      if (!isRegExp(separator)) {
        return nativeSplit.call(string, separator, lim);
      }
      var output = [];
      var flags = (separator.ignoreCase ? 'i' : '') +
                  (separator.multiline ? 'm' : '') +
                  (separator.unicode ? 'u' : '') +
                  (separator.sticky ? 'y' : '');
      var lastLastIndex = 0;
      // Make `global` and avoid `lastIndex` issues by working with a copy
      var separatorCopy = new RegExp(separator.source, flags + 'g');
      var match, lastIndex, lastLength;
      while (match = regexpExec.call(separatorCopy, string)) {
        lastIndex = separatorCopy.lastIndex;
        if (lastIndex > lastLastIndex) {
          output.push(string.slice(lastLastIndex, match.index));
          if (match.length > 1 && match.index < string.length) arrayPush.apply(output, match.slice(1));
          lastLength = match[0].length;
          lastLastIndex = lastIndex;
          if (output.length >= lim) break;
        }
        if (separatorCopy.lastIndex === match.index) separatorCopy.lastIndex++; // Avoid an infinite loop
      }
      if (lastLastIndex === string.length) {
        if (lastLength || !separatorCopy.test('')) output.push('');
      } else output.push(string.slice(lastLastIndex));
      return output.length > lim ? output.slice(0, lim) : output;
    };
  // Chakra, V8
  } else if ('0'.split(undefined, 0).length) {
    internalSplit = function (separator, limit) {
      return separator === undefined && limit === 0 ? [] : nativeSplit.call(this, separator, limit);
    };
  } else internalSplit = nativeSplit;

  return [
    // `String.prototype.split` method
    // https://tc39.github.io/ecma262/#sec-string.prototype.split
    function split(separator, limit) {
      var O = requireObjectCoercible(this);
      var splitter = separator == undefined ? undefined : separator[SPLIT];
      return splitter !== undefined
        ? splitter.call(separator, O, limit)
        : internalSplit.call(String(O), separator, limit);
    },
    // `RegExp.prototype[@@split]` method
    // https://tc39.github.io/ecma262/#sec-regexp.prototype-@@split
    //
    // NOTE: This cannot be properly polyfilled in engines that don't support
    // the 'y' flag.
    function (regexp, limit) {
      var res = maybeCallNative(internalSplit, regexp, this, limit, internalSplit !== nativeSplit);
      if (res.done) return res.value;

      var rx = anObject(regexp);
      var S = String(this);
      var C = speciesConstructor(rx, RegExp);

      var unicodeMatching = rx.unicode;
      var flags = (rx.ignoreCase ? 'i' : '') +
                  (rx.multiline ? 'm' : '') +
                  (rx.unicode ? 'u' : '') +
                  (SUPPORTS_Y ? 'y' : 'g');

      // ^(? + rx + ) is needed, in combination with some S slicing, to
      // simulate the 'y' flag.
      var splitter = new C(SUPPORTS_Y ? rx : '^(?:' + rx.source + ')', flags);
      var lim = limit === undefined ? MAX_UINT32 : limit >>> 0;
      if (lim === 0) return [];
      if (S.length === 0) return callRegExpExec(splitter, S) === null ? [S] : [];
      var p = 0;
      var q = 0;
      var A = [];
      while (q < S.length) {
        splitter.lastIndex = SUPPORTS_Y ? q : 0;
        var z = callRegExpExec(splitter, SUPPORTS_Y ? S : S.slice(q));
        var e;
        if (
          z === null ||
          (e = min(toLength(splitter.lastIndex + (SUPPORTS_Y ? 0 : q)), S.length)) === p
        ) {
          q = advanceStringIndex(S, q, unicodeMatching);
        } else {
          A.push(S.slice(p, q));
          if (A.length === lim) return A;
          for (var i = 1; i <= z.length - 1; i++) {
            A.push(z[i]);
            if (A.length === lim) return A;
          }
          q = p = e;
        }
      }
      A.push(S.slice(p));
      return A;
    }
  ];
}, !SUPPORTS_Y);