Answers for "Javascript key exists"

16

Javascript key exists

var person={"name":"Billy","age":20}
person.hasOwnProperty("name"); // true
person.hasOwnProperty("sex"); // false
Posted by: Guest on July-22-2019
5

javascript hashtable contains key

if (obj.hasOwnProperty("key1")) {
  ...
}
Posted by: Guest on March-01-2020
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
8

check if a key exists in an object javascript

"key" in obj // true, regardless of the actual value
Posted by: Guest on March-30-2020
2

how to check if a key exists in an object javascript

!("key" in obj) // true if "key" doesn't exist in object
!"key" in obj   // ERROR!  Equivalent to "false in obj"
Posted by: Guest on November-25-2020
-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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