如何在函数外使用变量

Question

I have this code in React Native:

inApp1.get('isFullVersionBought').then((data) => {
    console.log(data);
    let fullversionbought = data;
});

How i can use fullversionbought variable outside this function? Thanks.

Answer 1

You have to define the variable outside of the function, not inside as it is in your code sample.

var fullversionbought;
inApp1.get('isFullVersionBought').then((data) => {
    console.log(data);
    fullversionbought = data;
});

Javascript uses lexical scope at compile time.

Answer 2

Define the variable "fullbersionbought" outside the function first, then assign its value from within the function.

The keyword "let", by its very definition, means scope the variable as block local. They only persist while that particular function is running.

Answer 3

You can not use local variables out side the function.Thats why we have instance variables.

Add an instance variable to that class and fill the data in this function

Answer 4

The variable will be useless until it gets the data. To avoid waiting for the variable to be populated, I would recommend to use a component state. In that case, once you receive the data, you will update the state of the component:

constructor() {
  this.state = {
    fullversionbought: {}
  };

  this.getData():
}

getData() {
inApp1.get('isFullVersionBought').then((data) => {
    this.setState({
      fullversionbought: data
    });
});
}