TypeScript 2.8.3 Type must have a Symbol.iterator method that returns an iterator

this has helped me.
in tsconfig, add this :

{
    "compilerOptions": {
        "lib": [
            "es5", "es6", "dom", "dom.iterable"
        ]
    }
}

This is required for tsconfig to know which interfaces to import while transpiling your code.

dom.iterable includes all the interfaces mentioned here : https://github.com/microsoft/TypeScript/blob/master/lib/lib.dom.iterable.d.ts

Also thanks to @domlas for mentioning this. I already upvoted his comment so that it is treated as default reason.