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optional chaining

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Original file line number	Diff line number	Diff line change
`@@ -390,3 +390,25 @@ console.log(age);`
`390`	`390`	`// expected output: "0"`
`391`	`391`	```
`392`	`392`
	`393`	`+# Optional chaining`
	`394`	+```javascript
	`395`	`+`
	`396`	`+constcar= {}`
	`397`	`+constcarColor=car.name.color`
	`398`	`+console.log(carColor);`
	`399`	`+// error- "Uncaught TypeError: Cannot read property 'carColor' of undefined`
	`400`	`+`
	`401`	`+//In JavaScript, you can first check if an object exists, and then try to get one of its properties, like this:`
	`402`	`+constcarColor= car&&car.name&&car.name.color;`
	`403`	`+console.log(carColor);`
	`404`	`+//undefined- no error`
	`405`	`+`
	`406`	`+`
	`407`	`+//Now this new optional chaining operator will let us be even more fancy:`
	`408`	`+`
	`409`	`+constnewCarColor= car?.name?.color;`
	`410`	`+console.log(newCarColor)`
	`411`	`+//undefined- no error`
	`412`	`+`
	`413`	`+//You can use this syntax today using @babel/plugin-proposal-optional-chaining`
	`414`	+```

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