How to access 'this' inside a callback function in Typescript? [duplicate]

问题

This question already has answers here:

How to access the correct `this` inside a callback? (10 answers)

Closed 3 years ago.

I am trying to set a variable declared at the beginning of the class (a boolean) to true once a callback is called, but I keep getting a TypeScript erorr.

Here is the error:

TypeError: Cannot set property 'nonReceived' of undefined

Here is my code:

  finalizeToken(){
  braintree.setup(JSON.parse(this.finalToken), 'dropin', {
     container: 'dropin-container',
     defaultFirst: true,
      form: 'checkout-form',
      onPaymentMethodReceived: function (obj) {
        this.nonReceived = true;
      localStorage.setItem('nonce', obj.nonce);
    }
  });  
}

The brintree-setup connect to Braintree Payments, and awaits user payment info. Once they submit the form, I need the variable "this.nonReceived" to be set to true.

回答1:

If you use ES5 syntax you could use function(){}.bind(this) to bind the callback with the context but with Typescript you can use ES6 syntax and use arrow function (parameters) => {function_body} which bind current context implicitly.

来源：https://stackoverflow.com/questions/40353503/how-to-access-this-inside-a-callback-function-in-typescript