JavaScript with-like function

_with.js

var obj = {
    "ralph" : 1,
    "jon" : 2,
    "alex" : 3
};

function _with( fn, data ) {
   
    var keys   = Object.keys( data ),
        values = keys.map(function( key ) {
            return data[key];
        });
 
    new Function("(function(" + keys.join() + ") { return (" + fn.toString() + ")() }).apply(this, arguments)").apply( this, values );
}

_with(function() {
    console.log( ralph, jon, alex ); // 1, 2, 3
}, obj);

I think this has difficulty with closures. i.e. your generated function can't access any closure-scope variables from the input function.

That's a great point @benvinegar. There are also some other inconsistencies, such as, mutating properties made available by the _with function won't modify the obj passed in.

This was concocted as an alternative to using with for a templating library, which, for that use case, these inconsistencies may be advantageous, or moot.