JavaScript JSON : Object

Contains methods for encoding and decoding JSON strings.

Spec

JSON Methods

parse 2 variants

parse(str : String) : Object

Parses the specified string of JSON and converts it to an Object.

Example:

var x = JSON.parse('{"foo": 1, "bar": 2}');
console.log(x.foo);
console.log(x.bar);

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Results:

Spec

parse(str : String, reviver : Function) : Object

reviver(key : String, value : String) : Object

Parses the specified string of JSON and converts it to an Object. reviver will be called for each parsed key/value pair and the function's return value is used in place of the value.

Example:

var reviver = function(key, value) {
  console.log('reviver called with key="' + key + '", value=' + value);
  if (key === 'foo') {
    return value * 10;
  }
  return value;
};
var x = JSON.parse('{"foo": 1, "bar": 2}', reviver);
console.log(x.foo);
console.log(x.bar);

Run

Results:

Spec

stringify 3 variants

stringify(value : Object) : String

Converts value to a JSON string. If value has a toJSON() method on it, the return value of that method will be used.

Example:

var x = { foo: 1, bar: 2 };
console.log(JSON.stringify(x));

x.toJSON = function() {
  return { baz: 3 };
};
console.log(JSON.stringify(x));

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Results:

Spec

stringify(value : Object, keyNames : Array<String>, [indent : String]) : String

Converts value to a JSON string. If keyNames is not null, only key/value pairs where the key is in keyNames will be in the JSON string. If indent is specified, each key/value pair will be on a new line with the indent string before the key.

Example:

var x = { foo: 1, bar: 2 };
console.log(JSON.stringify(x, ['foo']));

console.log(JSON.stringify(x, null, '  '));

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Results:

Spec

stringify(value : Object, replacer : Function, [indent : String]) : String

replacer(key : String, value : Object) : String

Converts value to a JSON string. The replacer function is called for each key/value pair and the return value is used as the value in the final string. If indent is specified, each key/value pair will be on a new line with the indent string before the key.

Example:

var x = { foo: 1, bar: 2 };

var replacer = function(key, value) {
  console.log('replacer called with key="' + key + '", value=' + value, ', this=' + this);
  if (key === 'foo') return value * 10;
  return value;
}
console.log(JSON.stringify(x, replacer, ' '));

// If the object has a toJSON method, that will be called
// before calling the replacer. The original object is
// available as 'this[key]' inside replacer.
// Note, the replacer must be a 'function() {}' instead of
// '=>' function to get the correct 'this'.
x = { foo: 1, bar: 2, toJSON() { return 'my toJSON'; } };

replacer = function(key, value) {
  console.log('replacer called with key="' + key + '", value=' + value, ', (this[key]===x)=' + (this[key]=== x));
  return value;
}
console.log(JSON.stringify(x, replacer, ' '));

Run

Results:

Spec

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