unicorn/prefer-includes

tags.indexOf("draft") !== -1 asks for a position and then throws it away. tags.includes("draft") asks the question you mean, and there's no -1, 0, > or >= to get wrong.

The rule reports !== -1, != -1, > -1, >= 0, === -1, == -1 and < 0 after a call to indexOf(). It doesn't know types, so it reports any object with an indexOf method.

Configure

Off by default. To turn it on:

[lint.rules]
"unicorn/prefer-includes" = "error" # or "warn"

Examples

Reported:

if (tags.indexOf("draft") !== -1) {
  hide(post);
}

if (email.indexOf("@") < 0) {
  reject(email);
}

Not reported:

if (tags.includes("draft")) {
  hide(post);
}

if (!email.includes("@")) {
  reject(email);
}

Code that uses the position is fine:

const at = email.indexOf("@");
const hasName = email.indexOf("@") > 0;