CODEWITHSUNDEEP
javascript
GROVER.
GROVER.

Reputation: 4378

javascript cannot find a method which exists

I have a pretty simple function declared in my JavaScript file, which is just supposed to return whether or not the validation has begun:

window.Validator = function(){
    this._started = false;
    this.started = function(){
        return this._started;
    };
}

Validator.started();

However, when I call Validator.started(), even though it's literally directly after the declaration, it will throw the error:

Uncaught TypeError: Validator.started is not a function

Really scratching my head with this one and have no idea why it isn't working.

Upvotes: 0

Views: 78

Answers (3)

sfy
sfy

Reputation: 3228

this in a function without 'use strict' points to the global object, that is window.

So your this.started = function(){...} is defined on the window object. Of course, it is only defined after the Validator is called.

So this code works, though it may not how you want to use it.

window.Validator = function(){
    this._started = false;
    this.started = function(){
        return this._started;
    };
}

Validator();
started();
console.log(_started);

If you do use 'use strict', this is undefined in the function definition area. You need to create an Object of Validator, this would be the object when you call the method.

Upvotes: 0

Sergei Martianov
Sergei Martianov

Reputation: 301

this is a context. Or simply, it is an object which is on the left of dot. For example:

let v = new Validator();
v.started(); // v will be 'this' in your method

Your code:

Validator.started();

It means, that started() is a static method of Validator (method of exactly function Validator()). You have to write code as I write above. Or:

window.Validator = function() {};
Validator._started = false;
Validator.started = function() {
    return this._started;
};
console.log(Validator.started());

Here _started is a static property and started() is a static method of Validator().

Upvotes: 1

Grigory Babajanyan
Grigory Babajanyan

Reputation: 195

You should create an instance of your Validator

new Validator().started()

Upvotes: 7

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