object-wrapper

object-wrapper v1.0.1

Wraps all of an object's functions in a wrapper of your choosing.

API

The object-wrapper package is a single function that returns the wrapped object:

wrapper(object, wrapFcn, objectName, shouldAttachWrappersToObject);

The options to this function are as follows:

• object: Object | Function: The object (or function) that should be wrapped.
• wrapFcn: Function: A function invoked each time a wrapped function is run. It receives the following arguments:
  • functionInfo: Object: An object literal with the following fields:
    • namespace: Object: An object representing the namespace of the function, e.g. Dropbox.Client
    • namespaceName: String: A string name for the namespace of the function, e.g. "Dropbox.Client"
    • originalFcn: Function: The original, non-wrapped function, e.g. Dropbox.Client.readFile
    • originalFcnName: String: The original function name, e.g. "readFile";
  • args: Arguments object: The arguments passed to the function.
  • isConstructor: Boolean: True if the function was called with the new keyword, false otherwise.
  • callingFcn: Function: The caller of your wrapping function. Useful if you wish to trim stack traces passing through your wrapper.
• (Optional) objectName: String: The name for the object, e.g. "Dropbox". Used to construct "namespaceName".
• (Optional) shouldAttachWrappersToObject: Boolean: Determines if wrapper should return a new object, or place wrappers on the original object. Defaults to false.

The function returns the wrapped object.

Examples

Wrap the assert library to appropriately throw exceptions through the Mocha test runner:

var wrapper = require('object-wrapper').default;
var mocha = require('mocha');
// Permits calling a constructor via fcn.apply.
function construct(constructor, args) {
    function F() : void {
        constructor.apply(this, args);
    }
    F.prototype = constructor.prototype;
    return new F();
}
var wrappedAssert = wrapper(require('assert'), function (funcInfo, args, isConstructor) {
    try {
        if (!isConstructor) {
            return funcInfo.originalFcn.apply(funcInfo.namespace, args);
        } else {
            // Wrapped function called as a constructor. For the assert library, this occurs when
            // new assert.AssertionError objects are constructed.
            return construct(funcInfo.originalFcn, args);
        }
    } catch (e) {
        mocha.throwError(e);
    }
  }
}, 'assert' /* Name to use for root object in fcnInfo objects */);

Limitations

Does not wrap functions on the prototype of the passed-in function. The prototype must be wrapped separately.