Answers for "how to check if a specific key exists in an object"

6

javascript check if key exists in object

"key" in obj // true, regardless of the actual value

If you want to check if a key doesn't exist, remember to use parenthesis:
!("key" in obj) // true if "key" doesn't exist in object
!"key" in obj   // ERROR!  Equivalent to "false in obj"

Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty:
obj.hasOwnProperty("key") // true
Posted by: Guest on October-01-2020
-1

js check if object key exists

var obj = { key: undefined };
obj["key"] !== undefined // false, but the key exists!
Posted by: Guest on July-23-2020

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