es.number.constructor.js

'use strict';
var DESCRIPTORS = require('../internals/descriptors');
var global = require('../internals/global');
var isForced = require('../internals/is-forced');
var redefine = require('../internals/redefine');
var has = require('../internals/has');
var classof = require('../internals/classof-raw');
var inheritIfRequired = require('../internals/inherit-if-required');
var toPrimitive = require('../internals/to-primitive');
var fails = require('../internals/fails');
var create = require('../internals/object-create');
var getOwnPropertyNames = require('../internals/object-get-own-property-names').f;
var getOwnPropertyDescriptor = require('../internals/object-get-own-property-descriptor').f;
var defineProperty = require('../internals/object-define-property').f;
var trim = require('../internals/string-trim').trim;

var NUMBER = 'Number';
var NativeNumber = global[NUMBER];
var NumberPrototype = NativeNumber.prototype;

// Opera ~12 has broken Object#toString
var BROKEN_CLASSOF = classof(create(NumberPrototype)) == NUMBER;

// `ToNumber` abstract operation
// https://tc39.github.io/ecma262/#sec-tonumber
var toNumber = function (argument) {
  var it = toPrimitive(argument, false);
  var first, third, radix, maxCode, digits, length, index, code;
  if (typeof it == 'string' && it.length > 2) {
    it = trim(it);
    first = it.charCodeAt(0);
    if (first === 43 || first === 45) {
      third = it.charCodeAt(2);
      if (third === 88 || third === 120) return NaN; // Number('+0x1') should be NaN, old V8 fix
    } else if (first === 48) {
      switch (it.charCodeAt(1)) {
        case 66: case 98: radix = 2; maxCode = 49; break; // fast equal of /^0b[01]+$/i
        case 79: case 111: radix = 8; maxCode = 55; break; // fast equal of /^0o[0-7]+$/i
        default: return +it;
      }
      digits = it.slice(2);
      length = digits.length;
      for (index = 0; index < length; index++) {
        code = digits.charCodeAt(index);
        // parseInt parses a string to a first unavailable symbol
        // but ToNumber should return NaN if a string contains unavailable symbols
        if (code < 48 || code > maxCode) return NaN;
      } return parseInt(digits, radix);
    }
  } return +it;
};

// `Number` constructor
// https://tc39.github.io/ecma262/#sec-number-constructor
if (isForced(NUMBER, !NativeNumber(' 0o1') || !NativeNumber('0b1') || NativeNumber('+0x1'))) {
  var NumberWrapper = function Number(value) {
    var it = arguments.length < 1 ? 0 : value;
    var dummy = this;
    return dummy instanceof NumberWrapper
      // check on 1..constructor(foo) case
      && (BROKEN_CLASSOF ? fails(function () { NumberPrototype.valueOf.call(dummy); }) : classof(dummy) != NUMBER)
        ? inheritIfRequired(new NativeNumber(toNumber(it)), dummy, NumberWrapper) : toNumber(it);
  };
  for (var keys = DESCRIPTORS ? getOwnPropertyNames(NativeNumber) : (
    // ES3:
    'MAX_VALUE,MIN_VALUE,NaN,NEGATIVE_INFINITY,POSITIVE_INFINITY,' +
    // ES2015 (in case, if modules with ES2015 Number statics required before):
    'EPSILON,isFinite,isInteger,isNaN,isSafeInteger,MAX_SAFE_INTEGER,' +
    'MIN_SAFE_INTEGER,parseFloat,parseInt,isInteger'
  ).split(','), j = 0, key; keys.length > j; j++) {
    if (has(NativeNumber, key = keys[j]) && !has(NumberWrapper, key)) {
      defineProperty(NumberWrapper, key, getOwnPropertyDescriptor(NativeNumber, key));
    }
  }
  NumberWrapper.prototype = NumberPrototype;
  NumberPrototype.constructor = NumberWrapper;
  redefine(global, NUMBER, NumberWrapper);
}