Why doesn't JSON.stringify display object properties that are functions?

Question

Why doesn't JSON.stringify() display prop2?

var newObj = {
  prop1: true,
  prop2: function(){
    return "hello";
  },
  prop3: false
};

alert( JSON.stringify( newObj ) ); // prop2 appears to be missing

alert( newObj.prop2() ); // prop2 returns "hello"

for (var member in newObj) {
    alert( member + "=" + newObj[member] ); // shows prop1, prop2, prop3
}

JSFIDDLE: http://jsfiddle.net/egret230/efGgT/

Answer 1

Because JSON cannot store functions. According to the spec, a value must be one of:

_{(source: json.org)}

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As a side note, this code will make the functions noticed by JSON.stringify:

Function.prototype.toJSON = function() { return "Unstorable function" }