Rule: strict-comparisons

Only allow comparisons between primitives.

Rationale

When using comparison operators to compare objects, they compare references and not values. This is often done accidentally. With this rule, >, >=, <, <= operators are only allowed when comparing numbers. ===, !== are allowed for number string and boolean types and if one of the operands is null or undefined.

Notes:

Requires Type Info

Config

One of the following arguments may be optionally provided:

allow-object-equal-comparison allows != == !== === comparison between any types.
allow-string-order-comparison allows > < >= <= comparison between strings.

Config examples

"strict-comparisons": true

"strict-comparisons": [
  true,
  {
    "allow-object-equal-comparison": false,
    "allow-string-order-comparison": false
  }
]

Schema

{
  "type": "object",
  "properties": {
    "allow-object-equal-comparison": {
      "type": "boolean"
    },
    "allow-string-order-comparison": {
      "type": "boolean"
    }
  }
}

Code examples:

Disallows usage of comparison operators with non-primitive types.

"rules": { "strict-comparisons": true }

Passes

const object1 = {};
const object2 = {};
if (isEqual(object1, object2)) {}

Fails

const object1 = {};
const object2 = {};
if (object1 === object2) {}

Allows equality operators to be used with non-primitive types, while still disallowing the use of greater than and less than.

"rules": { "strict-comparisons": [true, {  "allow-object-equal-comparison": true }] }

Passes

const object1 = {};
const object2 = {};
if (object1 === object2) {}

Fails

const object1 = {};
const object2 = {};
if (object1 < object2) {}

Allows ordering operators to be used with string types.

"rules": { "strict-comparisons": [true, {  "allow-string-order-comparison": true }] }

Passes

const string1 = "";
const string2 = "";
if (string1 < string2) {}

Fails

const object1 = {};
const object2 = {};
if (object1 < object2) {}