Javascript JSON.parse "0x" string strange conversion

function sample2() {
  // Ref: https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse#%E3%83%9D%E3%83%AA%E3%83%95%E3%82%A3%E3%83%AB
  var rx_one = /^[],:{}s]*$/;
  var rx_two = /\(?:["\/bfnrt]|u[0-9a-fA-F]{4})/g;
  var rx_three = /"[^"\nr]*"|true|false|null|-?d+(?:.d*)?(?:[eE][+-]?d+)?/g;
  var rx_four = /(?:^|:|,)(?:s*[)+/g;
  var rx_dangerous = /[u0000u00adu0600-u0604u070fu17b4u17b5u200c-u200fu2028-u202fu2060-u206fufeffufff0-uffff]/g;
  JSON.parse = function (text, reviver) {

    // The parse method takes a text and an optional reviver function, and returns
    // a JavaScript value if the text is a valid JSON text.

    var j;

    function walk(holder, key) {

      // The walk method is used to recursively walk the resulting structure so
      // that modifications can be made.

      var k;
      var v;
      var value = holder[key];
      if (value && typeof value === "object") {
        for (k in value) {
          if (Object.prototype.hasOwnProperty.call(value, k)) {
            v = walk(value, k);
            if (v !== undefined) {
              value[k] = v;
            } else {
              delete value[k];
            }
          }
        }
      }
      return reviver.call(holder, key, value);
    }

    // Parsing happens in four stages. In the first stage, we replace certain
    // Unicode characters with escape sequences. JavaScript handles many characters
    // incorrectly, either silently deleting them, or treating them as line endings.

    text = String(text);
    rx_dangerous.lastIndex = 0;
    if (rx_dangerous.test(text)) {
      text = text.replace(rx_dangerous, function (a) {
        return (
          "\u" +
          ("0000" + a.charCodeAt(0).toString(16)).slice(-4)
        );
      });
    }

    // In the second stage, we run the text against regular expressions that look
    // for non-JSON patterns. We are especially concerned with "()" and "new"
    // because they can cause invocation, and "=" because it can cause mutation.
    // But just to be safe, we want to reject all unexpected forms.

    // We split the second stage into 4 regexp operations in order to work around
    // crippling inefficiencies in IE's and Safari's regexp engines. First we
    // replace the JSON backslash pairs with "@" (a non-JSON character). Second, we
    // replace all simple value tokens with "]" characters. Third, we delete all
    // open brackets that follow a colon or comma or that begin the text. Finally,
    // we look to see that the remaining characters are only whitespace or "]" or
    // "," or ":" or "{" or "}". If that is so, then the text is safe for eval.

    if (
      rx_one.test(
        text
          .replace(rx_two, "@")
          .replace(rx_three, "]")
          .replace(rx_four, "")
      )
    ) {

      // In the third stage we use the eval function to compile the text into a
      // JavaScript structure. The "{" operator is subject to a syntactic ambiguity
      // in JavaScript: it can begin a block or an object literal. We wrap the text
      // in parens to eliminate the ambiguity.

      j = eval("(" + text + ")");

      // In the optional fourth stage, we recursively walk the new structure, passing
      // each name/value pair to a reviver function for possible transformation.

      return (typeof reviver === "function") ?
        walk({
          "": j
        }, "") :
        j;
    }

    // If the text is not JSON parsable, then a SyntaxError is thrown.

    throw new SyntaxError("JSON.parse");
  };


  var content = '{"data":{"artemis_ids":{},"symbols":{"0XBTC":{"price":2.37}}}}';

  var sample1 = JSON.stringify(JSON.parse(content));
  var sample2 = Object.keys(JSON.parse(content).data.symbols);

  console.log(sample1); // <--- {"data":{"artemis_ids":{},"symbols":{"0XBTC":{"price":2.37}}}}
  console.log(sample2); // <--- [0XBTC]
}

sample2();