JSON.stringify()

JSON.stringify() converts a value to JSON notation representing it:

• Properties of non-array objects are not guaranteed to be stringified in any particular order. Do not rely on ordering of properties within the same object within the stringification.
• Boolean, Number, and String objects are converted to the corresponding primitive values during stringification, in accord with the traditional conversion semantics.
• If undefined, a function, or a symbol is encountered during conversion it is either omitted (when it is found in an object) or censored to null (when it is found in an array). JSON.stringify can also just return undefined when passing in "pure" values like JSON.stringify(function(){}) or JSON.stringify(undefined).
• All symbol-keyed properties will be completely ignored, even when using the replacer function.
• Non-enumerable properties will be ignored

JSON.stringify({});                  // '{}'
JSON.stringify(true);                // 'true'
JSON.stringify('foo');               // '"foo"'
JSON.stringify([1, 'false', false]); // '[1,"false",false]'
JSON.stringify({ x: 5 });            // '{"x":5}'

JSON.stringify(new Date(2006, 0, 2, 15, 4, 5)) 
// '"2006-01-02T15:04:05.000Z"'

JSON.stringify({ x: 5, y: 6 });
// '{"x":5,"y":6}' or '{"y":6,"x":5}'
JSON.stringify([new Number(1), new String('false'), new Boolean(false)]);
// '[1,"false",false]'

JSON.stringify({ x: [10, undefined, function(){}, Symbol('')] }); 
// '{"x":[10,null,null,null]}' 
 
// Symbols:
JSON.stringify({ x: undefined, y: Object, z: Symbol('') });
// '{}'
JSON.stringify({ [Symbol('foo')]: 'foo' });
// '{}'
JSON.stringify({ [Symbol.for('foo')]: 'foo' }, [Symbol.for('foo')]);
// '{}'
JSON.stringify({ [Symbol.for('foo')]: 'foo' }, function(k, v) {
  if (typeof k === 'symbol') {
    return 'a symbol';
  }
});
// '{}'

// Non-enumerable properties:
JSON.stringify( Object.create(null, { x: { value: 'x', enumerable: false }, 

                                      y: { value: 'y', enumerable: true } }) );
// '{"y":"y"}'

----------------------------
alert(JSON.stringify(/[a-z]/g));  // {}

@reference_0_mozilla