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Understanding conditional operators in javascript

Conditional (Ternary) Operator (?):​

The ? symbol is part of the conditional (ternary) operator in JavaScript. It's used for creating conditional expressions. The syntax is condition ? expr1 : expr2. If the condition evaluates to true, expr1 is executed; otherwise, expr2 is executed. Example:

let age = 20;
let status = (age >= 18) ? 'adult' : 'minor';
console.log(status); // Output: 'adult'

Nullish Coalescing Operator (??):​

The ?? symbol is the nullish coalescing operator introduced in ECMAScript 2020 (ES11).

  • It's used to provide a default value for a variable if the variable is null or undefined.
  • It differs from the logical OR (||) operator in that it only checks for null or undefined, not other falsy values like 0, false, '', etc.
  • The syntax is expr1 ?? expr2. If expr1 is null or undefined, it evaluates to expr2.
  • Example:
let user = {
    name: 'John',
    age: 25,
    address: null
};

let address = user.address ?? 'Unknown';
console.log(address); // Output: 'Unknown'

In summary, ? is used for conditional expressions, while ?? is used for providing default values for nullish variables.