How do I check if an object has a key in JavaScript

Question

Which is the right thing to do   if  myObj  key      undefined    or  if  myObj  key      null    or  if  myObj  key

User · Accepted Answer

Try the JavaScript in operator   if   key  in myObj    And the inverse   if     key  in myObj     Be careful  The in operator matches all object keys  including those in the object s prototype chain   Use myObj hasOwnProperty  key   to check an object s own keys and will only return true if key is available on myObj directly   myObj hasOwnProperty  key     Unless you have a specific reason to use the in operator  using myObj hasOwnProperty  key   produces the result most code is looking for

User · Answer

You should use hasOwnProperty  For example   myObj hasOwnProperty  myKey      Note  If you are using ESLint  the above may give you an error for violating the no-prototype-builtins rule  in that case the workaround is as below   Object prototype hasOwnProperty call myObj   myKey

User · Answer

You should use hasOwnProperty  For example   myObj hasOwnProperty  myKey      Note  If you are using ESLint  the above may give you an error for violating the no-prototype-builtins rule  in that case the workaround is as below   Object prototype hasOwnProperty call myObj   myKey

User · Answer

You should use hasOwnProperty  For example   myObj hasOwnProperty  myKey      Note  If you are using ESLint  the above may give you an error for violating the no-prototype-builtins rule  in that case the workaround is as below   Object prototype hasOwnProperty call myObj   myKey

User · Answer

You should use hasOwnProperty  For example   myObj hasOwnProperty  myKey      Note  If you are using ESLint  the above may give you an error for violating the no-prototype-builtins rule  in that case the workaround is as below   Object prototype hasOwnProperty call myObj   myKey

[javascript] How do I check if an object has a key in JavaScript?

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