no-dupe-keys

When an object literal has the same key twice, the last value silently replaces the first. In a long object it's easy to add a key that's already there, and then one of the two has no effect.

A getter and a setter with the same name are a pair, so they're allowed.

This rule is on by default in JavaScript files. It's off in TypeScript files, where TypeScript reports the same mistake.

Configure#

On by default as an error. To turn it off:

[lint.rules]
"no-dupe-keys" = "off" # or "warn"

Examples#

const options = {
  timeout: 1000,
  retries: 3,
  timeout: 5000,
};

const options = {
  timeout: 5000,
  retries: 3,
};

Keys are compared by value, so "timeout" is the same key as timeout, and 0x1 is the same key as 1:

const options = {
  timeout: 1000,
  "timeout": 5000,
};

const labels = {
  1: "one",
  0x1: "uno",
};

A computed key such as [name] and a spread aren't compared, because their keys are only known at runtime:

const options = {
  timeout: 1000,
  [name]: 5000,
  ...overrides,
};