fix(VO): check if entry exists

Author: lessp

.prettierrc

@@ -1,7 +1,6 @@
 {
   "bracketSpacing": true,
   "jsxBracketSameLine": false,
-  "parser": "babylon",
   "printWidth": 80,
   "semi": false,
   "singleQuote": true,

package-lock.json

@@ -22,7 +22,8 @@
     "storybook": "start-storybook -p 9001 -c .storybook",
     "prepare": "npm run test && npm run test",
     "test": "jest",
-    "test:dev": "jest --watch"
+    "test:dev": "jest --watch",
+    "format": "prettier --config .prettierrc src"
   },
   "repository": {
     "type": "git",
@@ -36,8 +37,8 @@
   "homepage": "https://github.com/lessp/react-is-visible",
   "husky": {
     "hooks": {
-      "pre-commit": "npm test",
-      "pre-push": "npm test"
+      "pre-commit": "npm run format && npm test",
+      "pre-push": "npm run format && npm test"
     }
   },
   "peerDependencies": {
@@ -72,6 +73,7 @@
     "intersection-observer": "0.5.1",
     "jest": "24.1.0",
     "jest-dom": "3.1.2",
+    "prettier": "^2.0.5",
     "react": "^16.8.0",
     "react-dom": "^16.8.0",
     "react-testing-library": "5.9.0",

package.json

@@ -27,7 +27,7 @@ class IsVisible extends React.PureComponent {
     }
 
     if (isIntersecting && this.props.once) {
-      this.unwatch() 
+      this.unwatch()
     }
   }
 

src/IsVisible.js

@@ -2,8 +2,14 @@ let intersectionObserver
 let intersectionObserverOptions = {}
 const subscribers = new WeakMap()
 
-const handleIntersections = entries =>
-  entries.forEach(entry => subscribers.get(entry.target).call(null, entry))
+const handleIntersections = (entries) =>
+  entries.forEach((entry) => {
+    const maybeEntry = subscribers.get(entry.target)
+
+    if (maybeEntry) {
+      maybeEntry.call(null, entry)
+    }
+  })
 
 const getIntersectionObserver = () => {
   if (!intersectionObserver) {
@@ -16,7 +22,7 @@ const getIntersectionObserver = () => {
   return intersectionObserver
 }
 
-const setIntersectionObserverOptions = options => {
+const setIntersectionObserverOptions = (options) => {
   if (intersectionObserver) {
     return
   }
@@ -35,7 +41,7 @@ const watch = (domNode, callback) => {
   return () => unwatch(domNode)
 }
 
-const unwatch = domNode => {
+const unwatch = (domNode) => {
   intersectionObserver.unobserve(domNode)
   subscribers.delete(domNode)
 }

src/VisibilityObserver.js

@@ -6,7 +6,7 @@ import { useIsVisible } from '../'
 
 afterEach(cleanup)
 
-const FunctionalComponent = props => {
+const FunctionalComponent = (props) => {
   const nodeRef = useRef()
   const isVisible = useIsVisible(nodeRef)
 

src/__tests__/hook.spec.js

@@ -8,7 +8,7 @@ afterEach(cleanup)
 
 const FunctionalComponent = ({ isVisible, ...props }) => <h1 {...props} />
 const FunctionalComponentWithIsVisible = withIsVisible(FunctionalComponent)
-const FunctionalComponentHook = props => {
+const FunctionalComponentHook = (props) => {
   const nodeRef = useRef()
   const isVisible = useIsVisible(nodeRef)
 

src/__tests__/vo.spec.js

@@ -4,7 +4,7 @@ import VO from './VisibilityObserver'
 
 const defaultOptions = {
   once: false,
-};
+}
 
 function useIsVisible(nodeRef, { once } = defaultOptions) {
   const [isVisible, setVisible] = useState(false)

src/useIsVisible.js

@@ -4,18 +4,18 @@ import hoistNonReactStatic from 'hoist-non-react-statics'
 
 import IsVisible from './IsVisible'
 
-const getDisplayName = WrappedComponent =>
+const getDisplayName = (WrappedComponent) =>
   WrappedComponent.displayName || WrappedComponent.name || 'Component'
 
 const defaultOptions = {
   once: false,
-};
+}
 
-export const withIsVisible = (WrappedComponent,  { once } = defaultOptions)=> {
+export const withIsVisible = (WrappedComponent, { once } = defaultOptions) => {
   const WithIsVisible = ({ forwardedRef, ...props }) => (
     <IsVisible
       once={once}
-      children={isVisible => (
+      children={(isVisible) => (
         <WrappedComponent {...props} isVisible={isVisible} ref={forwardedRef} />
       )}
     />