@danielkalen/simplybind/comparison/dist/bower_components/aurelia-binding/src/scope.js

Magically simple, framework-less one-way/two-way data binding for frontend/backend in ~5kb.

interface OverrideContext {
  parentOverrideContext: OverrideContext;
  bindingContext: any;
}

// view instances implement this interface
interface Scope {
  bindingContext: any;
  overrideContext: OverrideContext;
}

export function createOverrideContext(bindingContext?: any, parentOverrideContext?: OverrideContext): OverrideContext {
  return {
    bindingContext: bindingContext,
    parentOverrideContext: parentOverrideContext || null
  };
}

export function getContextFor(name: string, scope: Scope, ancestor: number): any {
  let oc = scope.overrideContext;

  if (ancestor) {
    // jump up the required number of ancestor contexts (eg $parent.$parent requires two jumps)
    while (ancestor && oc) {
      ancestor--;
      oc = oc.parentOverrideContext;
    }
    if (ancestor || !oc) {
      return undefined;
    }
    return name in oc ? oc : oc.bindingContext;
  }

  // traverse the context and it's ancestors, searching for a context that has the name.
  while (oc && !(name in oc) && !(oc.bindingContext && name in oc.bindingContext)) {
    oc = oc.parentOverrideContext;
  }
  if (oc) {
    // we located a context with the property.  return it.
    return name in oc ? oc : oc.bindingContext;
  }
  // the name wasn't found.  return the root binding context.
  return scope.bindingContext || scope.overrideContext;
}

export function createScopeForTest(bindingContext: any, parentBindingContext?: any): Scope {
  if (parentBindingContext) {
    return {
      bindingContext,
      overrideContext: createOverrideContext(bindingContext, createOverrideContext(parentBindingContext))
    };
  }
  return {
    bindingContext,
    overrideContext: createOverrideContext(bindingContext)
  };
}