CODEWITHSUNDEEP
javascript
Aether W
Aether W

Reputation: 1

is JS able to overwrite Object's Getter method?

everyone:

as we all know, getting a nonexistent value from Object will got a "undefined", is there any way to throw an error instead of return a undefined?

for instance:

var a= {example:"example"};
//do something here

a.b  //error throw instead of "undefined"

thx very much for helping.

Upvotes: 0

Views: 321

Answers (3)

Don
Don

Reputation: 6882

Looking at the above example, if you are you trying to initialize the property "b" on the object a with a value after "a" has been defined, then you could just as easily do the following:

var a= {example:"example"};
//do something here

a.b = 'some value';
a.b  //now an error is not throw

Most Objects can be re-defined even after they have been initialized. Properties and methods can be added and removed once objects have been initialized. I say most, because it is possible to prevent objects from being extended/altered (using Object.preventExtension method). https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/preventExtensions

Upvotes: 0

Bhargav Ponnapalli
Bhargav Ponnapalli

Reputation: 9422

ES6 comes with Proxy Objects which will help you overload the dot operator. What this means is that you can invoke a function when you retrieve a property. This will allow you to check if the property is defined and if it isn't "throw" an error. Hope this helps. More info here

Upvotes: 0

Praveen
Praveen

Reputation: 236

Object.define property has a way to specify the get and set methods

look at the link below

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty

Object class has a method "hasOwnProperty" which could also be used to check if a property exists or not before trying to access it

Upvotes: 1

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