title: Firebase Storage check if value is null in JavaScript
body: <p>I want delete image only when storageId is not null.</p>
  
  <p>I checked for null like so and value is null but it's fired so exception says not found that image.</p>
  
  <p>How can I check if it's null?</p>
  
  <pre><code>  const data = snapshot.data();
    const ref = firebase.storage().ref();
    if (data.storageId != null) {
      ref.child('images').child(`${data.storageId}.jpg`).delete();
    }
  </code></pre>