¿Cómo usar Assert.isUndefined () y Assert.isNotUndefined () en YUI3?

I'm trying to test for the presence of a declared, defined function using the YUI3 Test framework. In Safari and FireFox, trying to use isNotUndefined, isUndefined, or isFunction fails. I expect those to throw an exception that can be handled by the test framework.

 Y.Assert.isNotUndefined(x, "fail message")
 ReferenceError: Can't find variable: x
 Y.Assert.isUndefined(x, "fail message")
 ReferenceError: Can't find variable: x
 Y.Assert.isFunction(x, "fail message")
 ReferenceError: Can't find variable: x

But, instead, I never get to see the failure messages, and the remainder of the tests do not run, because of the interpreter getting in the way... Doesn't that undermine the purpose of these functions, or am I misunderstanding the framework?

My intuition tells me that, given the code above and only the code above,

  Y.Assert.isUndefined(x, "fail message")

should continue on without an error (because x is undeclared) and

  Y.Assert.isNotUndefined(x, "fail message")

should log the message "fail message" (because x is undeclared).

However, because of the ReferenceError, there's no way (using those YUI3 methods) to test for undeclared objects. Instead, I'm left with some pretty ugly assertion code. I can't use

 ReferenceError: Can't find variable: x


 Y.assert( x !== undefined )
 ReferenceError: Can't find variable: x

which leaves me with

 Y.assert( typeof(x) !== "undefined" ) // the only working option I've found
 Assert Error: Assertion failed.

which is much less readable than


Again, I ask: Doesn't that undermine the purpose of these functions, or am I misunderstanding the framework?



is undeclared, and so not directly testable, while

 var x;

declares it, but leaves it undefined. Finally

 var x = function() {};

is both declared and defined.

I think that what's missing for me is the ability to easily say



preguntado el 09 de enero de 11 a las 03:01

Show the code, there's no variable in x thus the ReferenceError. -

Thank you, Ivo. I fully understand WHY I get a ReferenceError. The point is that because of the ReferenceError, I can't test to see whether a non-existent object is undefined within the YUI3 Test framework. -

2 Respuestas

OK, was a bit late yesterday guess I understand you question now, what you want to do is to check whether a variable was defined at all, right?

The only way to do this is typeof x === 'undefined'.

La typeof operator allows for non-existent variables to be used with it.

So in order to it to work, you need the above expression and plug that into a normal true/false assert.

For example (haven't used YUI3):

Y.Assert.isTrue(typeof x === 'undefined', "fail message"); // isUndefined
Y.Assert.isFalse(typeof x === 'undefined', "fail message"); // isNotUndefined

Respondido el 09 de enero de 11 a las 20:01

CONTEXT: I want to be able to distinguish among:

x // undeclared && undefined
var x; // declared && undefined
var x = 5; // declared && defined

So, the challenge here is that JavaScript doesn't readily distinguish between the first 2 cases, which I wanted to be able to do for teaching purposes. After a lot of playing and reading, there does seem to be a way to do it, at least within the context of a web browser and for global variables (not great restrictions, but...):

function isDeclared(objName) {
  return ( window.hasOwnProperty(objName) ) ? true : false;

function isDefined(objName) {
  return ( isDeclared(objName) && ("undefined" !== typeof eval(objName)) ) ? true : false;

I realize that the use of eval could be unsafe, but for the tightly controlled context in which I would use these functions, it's OK. All others, beware and see http://www.jslint.com/lint.html

isDeclared("x")  // false
isDefined("x")   // false

var x;
isDeclared("x")  // true
isDefined("x")   // false

var x = 5;
isDeclared("x")  // true
isDefined("x")   // true

Respondido 02 Feb 11, 01:02

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