Best way to handle null values in ReactJS?

Question

I'm accessing an API with ReactJS. What is the best way to stop React Component crashing when it's accessing a property in the object provided by the API that may be 'undefined'?

An example of an error is:

TypeError: Cannot read property 'items' of undefined

Answer 1

• In simple function you do it simply by if statement.

if(typeof x !=='undefined' && typeof x.item !=='undefined'){

}

• in JSX you do it in this way.

render(){
return(
          <div>
          (typeof x !=='undefined' && typeof x.item !=='undefined')?
                <div>success</div>:           
                <div>fail</div>
          </div>
          )
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>

Answer 2

It looks like you're trying to access the property items of a variable x.

And if x is undefined, then calling x.items will give you the error you mentioned.

Doing a simple:

if (x) {
  // CODE here
}

or

if (x && x.items) { // ensures both x and x.items are not undefined
  // CODE here
}

EDIT:

You can now use Optional Chaining, which looks sweet:

if (x?.items)