E0146: missing ':' in conditional expression

The ? : ternary operator has three parts: the condition, the expression if true, and the expression if false. It is a syntax error to omit the expression if false:

for (let i = 1; i <= 100; ++i) {
  console.log(i % 15 ? i);
}

document.querySelector("form input")?focus();

To fix this error, write : followed by an expression:

for (let i = 1; i <= 100; ++i) {
  console.log(i % 15 ? i : "FizzBuzz");
}

Alternatively, write ?. instead of ? to access an object's property:

document.querySelector("form input")?.focus();

Introduced in quick-lint-js version 0.2.0.

Documentation for other errors