How can a Javascript object refer to values in itself?
This can be achieved by using constructor function instead of literal
var o = new function() {
this.foo = "it";
this.bar = this.foo + " works"
}
alert(o.bar)
Maybe you can think about removing the attribute to a function. I mean something like this:
var obj = {
key1: "it ",
key2: function() {
return this.key1 + " works!";
}
};
alert(obj.key2());
You can't refer to a property of an object before you have initialized that object; use an external variable.
var key1 = "it";
var obj = {
key1 : key1,
key2 : key1 + " works!"
};
Also, this is not a "JSON object"; it is a Javascript object. JSON is a method of representing an object with a string (which happens to be valid Javascript code).
One alternative would be to use a getter/setter methods.
For instance, if you only care about reading the calculated value:
var book = {}
Object.defineProperties(book,{
key1: { value: "it", enumerable: true },
key2: {
enumerable: true,
get: function(){
return this.key1 + " works!";
}
}
});
console.log(book.key2); //prints "it works!"
The above code, though, won't let you define another value for key2.
So, the things become a bit more complicated if you would like to also redefine the value of key2. It will always be a calculated value. Most likely that's what you want.
However, if you would like to be able to redefine the value of key2, then you will need a place to cache its value independently of the calculation.
Somewhat like this:
var book = { _key2: " works!" }
Object.defineProperties(book,{
key1: { value: "it", enumerable: true},
_key2: { enumerable: false},
key2: {
enumerable: true,
get: function(){
return this.key1 + this._key2;
},
set: function(newValue){
this._key2 = newValue;
}
}
});
console.log(book.key2); //it works!
book.key2 = " doesn't work!";
console.log(book.key2); //it doesn't work!
for(var key in book){
//prints both key1 and key2, but not _key2
console.log(key + ":" + book[key]);
}
Another interesting alternative is to use a self-initializing object:
var obj = ({
x: "it",
init: function(){
this.y = this.x + " works!";
return this;
}
}).init();
console.log(obj.y); //it works!