10.2.1.2.2 CreateMutableBinding

Undefined CreateMutableBinding(N:String, D:Boolean)

Create a property on the binding object with name N. The D parameter determines whether N can be deleted.

function CreateMutableBinding(N, D){
var envRec = this;
var bindings = envRec.bindingObject;
if (bindings.[[HasProperty]](N)) return; // "assert" bindings has no property N
var configValue = D;
bindings.[[DefineOwnProperty]](N, PD{[[Value]]:undefined, [[Enumerable]]:true, [[configurable]]:configValue}, false);
}