# Source: https://github.com/quick-lint/quick-lint-js/blob/master/docs/errors/E0287.md

# E0287: upper case letters compared with toLowerCase

Comparing the result of a function named `toLowerCase` to a string literal with
one or more upper case letters will always yield the same result.

```javascript
let x = "BaNaNa";

// always returns 'false'
if (x.toLowerCase() === "BANANA") {
} 

// always returns 'true'
if (x.toLowerCase() !== "BANANA") {
} 
```

Introduced in quick-lint-js version 2.9.0.