quick-lint-js

Find bugs in JavaScript programs.

E0074: '.' operator needs a key name; use + to concatenate strings; use [] to access with a dynamic key

The right-hand side of the . operator must be a property name or a private property name. It is an error for . to be followed by a literal:

const ages = {
  "strager": 29,
  "Elon Musk": 50,
};
console.log("Musk's age:", ages."Elon Musk");

const $favoriteLanguage = 'PHP';
console.log('I love ' . $favoriteLanguage);

To fix this error, access properties using [ ] instead of .:

const ages = {
  "strager": 29,
  "Elon Musk": 50,
};
console.log("Musk's age:", ages["Elon Musk"]);

Alternatively, concatenate strings using + instead of .:

const $favoriteLanguage = 'PHP';
console.log('I love ' + $favoriteLanguage);

Documentation for other errors