ES5 this.method is not a function

Question

I have a typescript 2 class that targets ES5. I\'m getting the err in the subject line in the console when I run it. The switch statement works fine, but increment() and decre

Answer 1

Make sure you bind this to your functions so that the value of this will be what you expect when you call the functions:

class MyClass extends React.Component{
  constructor() {
    super()
    this.increment = this.increment.bind(this)
    this.decrement = this.decrement.bind(this)
    this.buttonClick = this.buttonClick.bind(this)
  }
  increment() {
    console.log('increment()')
  }
  decrement() {
    console.log('decrement()')
  }
  buttonClick(btn) {
    // ...
  }
}

You can also use property initialized arrow functions if you prefer:

class MyClass extends React.Component{
  increment = () => {
    console.log('increment()')
  }
  decrement = () => {
    console.log('decrement()')
  }
  buttonClick = (btn) => {
    // ...
  }
}