This simple proposal is inspired by an extension of Rhino that currently allows
to implement its syntax for anonymous Java interface implementation. Here an
example that creates an anonymous class implementing the Runnable interface and
defining the run method in an anonymous object literal that (mimicking a Java
code block) immediately following the constructor call:
var runnable = new java.lang.Runnable() {
run: function() {
}
};
When looking deeper into how Rhino achieves this syntax, I found out that it
simply appends the following anonymous object literal to the list of arguments
of whatever constructor came before. So the following code works in Rhino and
prints the content of the hello string to the console:
function Test(obj) {
print(obj.hello);
}
new Test() {
hello: 'Greetings, I am an anonymous object literal'
};
For the Illustrator scripting plugin http://scriptographer.org I came up with
the convention to (ab)use this non-standard feature to allow setting of
properties on freshly created objects, by extending the underlying Java proxy
objects to automatically detect such a passed object literal, iterate through
its properties and set them on the newly created object (In Scriptographer it
is then also removed from the argument list). Soon it became apparent that this
is very useful and also leads to cleaner code. I therefore started to wonder if
this would make sense as an syntax extension in ES5. Here another example.
function MyConstructor(param) {
print(param); // Should not print the object literal
}
var obj = new MyConstructor() {
property: 'This will be automatically set on the created object'
};
print(obj.property); // 'This will...created object'
So far I cannot see any syntax conflicts.
I am wondering what you all think of this proposal and look forward to your
thoughts.
Jürg
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