quick-lint-js

Find bugs in JavaScript programs.

E0136: cannot update variable with '+=' while declaring it

When declaring a variable with const, let, or var, you can set the variable's initial value using =. It is a syntax error to use a compound assignment operator instead of =:

let i = 0;
while (i < 100) {
  let i += 1;
  console.log(i % 15 ? i : "FizzBuzz");
}

const length *= Math.sqrt(x*x + y*y + z*z);

To fix this error, remove the let keyword:

let i = 0;
while (i < 100) {
  i += 1;
  console.log(i % 15 ? i : "FizzBuzz");
}

Alternatively, replace the compound assignment operator with =:

const length = Math.sqrt(x*x + y*y + z*z);

Documentation for other errors