I have a function that is bound to a React component:

```
    functionName(param1, param2 = this.state.field) {

    }

```

I've never heard of the 'this' keyword being used within a function signature in Javascript and am wondering if the context of 'this' will be the containing object or the global scope. Does this function need to be bound to the proper context before I can use 'this' properly within the signature?