The function angular.isDefined(obj) will fail to work when the variable "obj" is not defined

Question

The function angular.isDefined(obj) will fail to work when the variable "obj" is not defined

Typically, I find myself using the slightly cluttered typeof obj !== "undefined" expression. But recently, I came across the angular.isDefined(obj) function. According to the documentation, it should return false if the object is not defined. However, in my experience (specifically in Firefox), it simply throws an error saying "obj is not defined." Am I overlooking something here?

javascript angularjs

Answer 1

Answer №1

In summary: Although angular.isDefined(obj) is useful, it cannot completely replace the functionality of typeof.

Is there something I am overlooking?

I don't believe so. The typeof operator behaves differently than passing a variable to a function. While typeof won't throw an error if the variable doesn't exist, passing it to a function will. It's simply the nature of how JavaScript works.

As far as I know, typeof is unique in handling reference errors without throwing. However, if you find yourself needing to constantly check if a variable exists, it may be a sign of poor coding practice (unless it is necessary for certain functionalities like checking for third-party modules).

Here are some examples to illustrate the expected behavior:

var foo;
var bar = 42;

typeof foo !== 'undefined'; // false
typeof bar !== 'undefined'; // true
typeof baz !== 'undefined'; // false

isDefined(foo); // false
isDefined(bar); // true
isDefined(baz); // ReferenceError

Answer 2

In summary: Although angular.isDefined(obj) is useful, it cannot completely replace the functionality of typeof.

Is there something I am overlooking?

I don't believe so. The typeof operator behaves differently than passing a variable to a function. While typeof won't throw an error if the variable doesn't exist, passing it to a function will. It's simply the nature of how JavaScript works.

As far as I know, typeof is unique in handling reference errors without throwing. However, if you find yourself needing to constantly check if a variable exists, it may be a sign of poor coding practice (unless it is necessary for certain functionalities like checking for third-party modules).

Here are some examples to illustrate the expected behavior:

var foo;
var bar = 42;

typeof foo !== 'undefined'; // false
typeof bar !== 'undefined'; // true
typeof baz !== 'undefined'; // false

isDefined(foo); // false
isDefined(bar); // true
isDefined(baz); // ReferenceError

Answer 3

Answer №2

Trying to access a variable that is truly undefined in JavaScript will result in an error unless you use the typeof operator. The only way to check if a variable is defined is by using Angular.isDefined with properties. For example:

Angular.isDefined(window.obj);

This code will work fine because obj is an undefined property of window.

Answer 4

Trying to access a variable that is truly undefined in JavaScript will result in an error unless you use the typeof operator. The only way to check if a variable is defined is by using Angular.isDefined with properties. For example:

Angular.isDefined(window.obj);

This code will work fine because obj is an undefined property of window.

Answer 5

Answer №3

I attempted a solution like this:

try {
        if (angular.isDefined (obj.a.b)) {
            // perform actions on obj.a.b
        }
    } catch (e) {
        // handle situations where obj, obj.a, or obj.a.b is undefined
    }

By using this approach, I can avoid encountering exceptions when a referenced property in the object hierarchy is not defined.

Answer 6

I attempted a solution like this:

try {
        if (angular.isDefined (obj.a.b)) {
            // perform actions on obj.a.b
        }
    } catch (e) {
        // handle situations where obj, obj.a, or obj.a.b is undefined
    }

By using this approach, I can avoid encountering exceptions when a referenced property in the object hierarchy is not defined.

The function angular.isDefined(obj) will fail to work when the variable "obj" is not defined

Answer №1

Answer №2

Answer №3

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