Throw expressions

Baseline

Throw errors in expressions.

Type	TC39	CoreJS	Babel	Civet	JS+
Syntax	✅ Stage 2 View		✅ View	❌	✅ via Babel

JS+ TypeScript

const double = (x = throw new Error('double expects a number')) => {
  return x * 2;
}

double(); // Error: double expects a number

const double = (x: number) => {
  if (typeof x !== 'number') {
    throw new Error('double expects a number');
  }

  return x * 2;
}

In JavaScript throw expressions could also be used to throw errors on missing parameters.

const double = (x = throw new Error('double expects a number')) => {
  return x * 2;
};

double(); // Error: double expects a number