Reactjs how to convert string to object property : In a React project, I want to pass the property name dynamically.
I am able to pass a value as string, however when I try to either concatenate or add it to the object it doesn't work.

Here's an example:

    book = { title: 'Sample title', content : 'some content' } 

I access title like this : `return book.title`

I can see the passed variable correctly:

    const passedField = this.props.passedField;
 I want to access it like `return book.passedField` but I get undefined on console.

How can I achieve this?

