How to Solve “error TS2339: Property ‘<label>’ does not exist on type ‘{}’ “ in angular 5

In web application we used object( JSON). so I also tried to pass Json object to a method and used(print) it. but my first try fail because I got error what is mention in main title

this is my code which is my initial code

printFirstName(a={}){
   console.log(a.firstName);
}

problem: I getting an error

error TS2339: Property 'firstName' does not exist on type '{}'.

but I called printFistName() function like below

let a={firstName:'Jhone',age:26};
printFirstName(a);

Solution: I changed my printFirstName method “a.firstName” to “a[‘firstName’]” . This solve my error.

printFirstName(a={}){
   console.log(a['firstName']);
}

I hope this help you if you got this error try this way

thank you