prefer-for-of rule recommended on a node list

[mattferderer]

Bug Report

• TSLint version: 5.4.3
• TypeScript version: 2.3.4
• Running TSLint via: VSCode eg2.tslint

TypeScript code being linted

const items = document.getElementsByClassName("items")
for(let i =0; i < items.length; i++) {
  
}

with tslint.json configuration:

{
    "defaultSeverity": "error",
    "extends": [
        "tslint:recommended"
    ],
    "jsRules": {},
    "rules": {
      "semicolon": [true, "never"],
      "no-unnecessary-type-assertion": true
    },
    "rulesDirectory": []
}

Actual behavior

Receiving the error "Expected a 'for-of' loop instead of a 'for' loop with this simple iteration (prefer-for-of)

Expected behavior

A for of loop to my knowledge shouldn't be used on a NodeList as it's not supported widely & is also not part of any standard. TypeScript will complain if you do this. The same with a forEach loop.

[Jessidhia]

It is specified as iterable<Node> (https://dom.spec.whatwg.org/#interface-nodelist). If TypeScript does not allow you to iterate on it, then it's TypeScript that needs fixing.

Also note that core-js can polyfill iterators for most DOM collections, including NodeList.

If you need to be "safe" and avoid iterating on them directly, you could also wrap the NodeList-resulting call with Array.from.

[mattferderer]

@Kovensky do you run a specific tsconfig that allows TypeScript to do this or are you suggesting to request it as an issue for them?

My comment about it not being supported was based off of the MDN Specifications that state "forEach on NodeList is NOT a part of any standard". Maybe I'm misunderstanding that though.

[NN---]

@Kovensky It is iterable with ES6 support or with --downlevelIterators flag in TypeScript.
If you use ES5 mode , then it is not iterable using for..of.

I had to remove this rule due to this false positive.

[JoshuaKGoldberg]

Duplicate of #2021.