Run results for: JSON.stringify vs string concat

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:82.0) Gecko/20100101 Firefox/82.0

Browser: Firefox 82

Operating system: Mac OS X 10.16

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
JSON.stringify	1337722.0 Ops/sec
String concat	2697075.0 Ops/sec

Script Preparation code:

var object = {
  str_key: 'this is "a \nstring',
  num_key: 42,
  bool_key: true,
  array_key: [1, 2, 3]
};

function escapeForJSON(string) {
  let result = "";
  const length = string.length;
  for (let i = 0; i !== length; ++i) {
    // Obviously missing a few other characters to escape
    if (string.charAt(i) == '"') {
      result += '\\"';
    } else {
      result += string.charAt(i);
    }
  }
  return result;
}

function stringConcat(obj) {
  let result = '{"str_key":"';
  result += escapeForJSON(obj.str_key);
  result += '","num_key":';
  result += obj.num_key.toString();
  result += ',"bool_key":';
  result += obj.bool_key.toString();
  result += ',"array_key":[';
  const length = obj.array_key.length;
  if (length > 0) {
    result += obj.array_key[0].toString();
  }
  for (let i = 1; i < length; ++i) {
    result += ',';
    result += obj.array_key[i].toString();
  }
  result += ']}';
  return result;
}

Tests:

JSON.stringify
JSON.stringify(object);
String concat
stringConcat(object);

Run results for: JSON.stringify vs string concat

JSON.stringify

String concat