Do you know what will be the output of this code? console.log(JSON.stringify({ a: undefined, b: null, c: () => 1 }));

Why does JSON.stringify drop undefined and functions?

Do you know what will be the output of this code?

JavaScript

console.log(JSON.stringify({ a: undefined, b: null, c: () => 1 }));

Show answer and explanation

The answer is {"b":null}.

JSON supports null but not undefined or functions. Object properties with those values are left out. Inside arrays they become null instead.