quick-lint-js

Find bugs in JavaScript programs.

E0110: for-in loop expression cannot have semicolons

There are three kinds of for loops: C-style for loops (;), for-in loops, and for-of loops. It is a syntax error to write a for-in loop with a ;:

for (let i in 0; i < 100; ++i) {
  console.log(i % 15 ? i : "FizzBuzz");
}

let benchmarks = collectBenchmarks();
for (const name in benchmarks;) {
  runBenchmark(name, benchmarks[name]);
}

To fix this error, remove the in keyword in the C-style for loop:

for (let i = 0; i < 100; ++i) {
  console.log(i % 15 ? i : "FizzBuzz");
}

Alternatively, remove the extra ;:

let benchmarks = collectBenchmarks();
for (const name in benchmarks) {
  runBenchmark(name, benchmarks[name]);
}

Documentation for other errors