The

JSON.stringify()

will remove functions from a JavaScript object because

function

is not valid data type in

JSON

var obj = { name: "John", age: function () {return 30;}, city: "New York" };

// Functions and any other unsupported data types will be ignored
var myJSON = JSON.stringify(obj);
document.write(myJSON);

The result will be:

{"name":"John","city":"New York"}

As we can see, the

function

is removed. To solve this issue we can convert the function into

string

before running

stringify

var obj = { name: "John", age: function () {return 30;}, city: "New York" };
obj.age = obj.age.toString();
var myJSON = JSON.stringify(obj);
document.write(myJSON);

The result will be:

{"name":"John","age":"function () {return 30;}","city":"New York"}