best way to replace an eval( "new object()" )

Question

I m looking for the best way to replace eval( "new object();" )

The ugly source :

    //var type = window.$(droppedDomNode).data("shape");
    var type = "sankey.shape.Start";

    var figure = eval("new "+type+"();");
    
    // create a command for the undo/redo support
    var command = new draw2d.command.CommandAdd(this, figure, x, y);

The eval create a new sankey.shape.Start object.

I'm looking for best solution to replace this kind of code.

Thanks

Where does `sankey` come from? Is that an import or a global variable? — GOTO 0, Feb 10 '22 at 14:05
I mean, where is `sankey` defined in your code, do you know that? — GOTO 0, Feb 10 '22 at 14:11
Any way with Object.create("sankey.shape.Start") or a wrong solution ? — dterencio, Feb 10 '22 at 14:19
That doesn't work, the syntax would be Object.create(sankey.shape.Start.prototype)` (without double quotes) — GOTO 0, Feb 10 '22 at 14:23

score 5 · Answer 1 · answered Feb 10 '22 at 13:52

5

I'd build an object (mapping) of constructor functions.

const constructors = {
  "sankey.shape.Start": () => new sankey.shape.Start(),
  // etc... (this could be built programmatically)
};

Then,

const figure = constructors[type]();

answered Feb 10 '22 at 13:52

AKX

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1

Or `const constructors = { "sankey.shape.Start": sankey.shape.Start }; new constructors[type];`. – Sebastian Simon Feb 10 '22 at 13:56
I think, I need protect the object creation . What happend if I wish create "sankey.shape.badobject" – dterencio Feb 10 '22 at 14:23
You'd get a "undefined is not callable", since that key isn't in the mapping. – AKX Feb 10 '22 at 15:23

score 1 · Answer 2 · answered Feb 10 '22 at 13:58

You can split it and walk up the path from window if it is global

var foo = {
  bar: {
    world: 'baz',
  }
}

const getIt = (str, start = window) => {
  return str.split(/\./).reduce((o, k) => o[k], start);
}


const x = "foo.bar.world";
console.log(getIt(x))

best way to replace an eval( "new object()" )

2 Answers2