quick-lint-js

Find bugs in JavaScript programs.

E0034: redeclaration of variable

In a given function or {} block, a variable can only be declared multiple times if it is declared with var or function. Other types of variables can be declared only once:

let x, y, y, w;

const friends = loadFriends();
const friends = friends
  .filter(friend => friend.name !== "strager");

class Orange { name = "orange" }
class Orange { name = "banana" }

function jump(player, height) {
  let height = height || player.height/2;
}

To fix this error, assign to the existing variable, choose a different variable name, or delete the extra variable:

let x, y, z, w;

let friends = loadFriends();
friends = friends
  .filter(friend => friend.name !== "strager");

class Orange { name = "orange" }
class Banana { name = "banana" }

function jump(player, height) {
  height = height || player.height/2;
}

Documentation for other errors