doc.md

Better Mongo Id comparison

MongoDB is a popular NoSQL database. The primary key for each record (in javascript/typescript) is an ObjectId, a javascript object.

However, this has one major unexpected behavior:

const x = new ObjectId()
const y = new ObjectId(x.toString())
console.log(x.equals(y)) // true
console.log(x === y) // false

The fact that we have to use equals rather than the usual javascript operator. leads to many false negatives with no typescript / eslint warnings!

Proposed Solution:

this eslint rule that warns on id1 === id2. The rule should search the abstract syntax tree sending a warning for instances of the operator === where both the left-hand-side and right-hand-side could be ObjectId

const equalBad = (id1: ObjectId | null, id2: ObjectId | 2 | false) => {
  return id1 === id2 // triggers
}

const equalOk = (id1: ObjectId | string | null, id2: string | null) => {
  return  id1 === id2 // does not trigger
}