typescriptecmascript-6

How to iterate over keys of a generic object in TypeScript?

I need to iterate over a large object which is just typed as "object". It contains an unknown number of objects of the same type.

In older posts I had found solutions using a generator within a custom Symbol.iterator function to make the large object iterable with a for..of loop.

But it seems to me, now in 2017, just using Object.keys is actually easier:

Object.keys(bigObject).forEach((key:string)=>{
console.log(bigObject[key]);
});

This actually runs just fine! But the TypeScript compiler keeps giving me the error "error TS7017: Element implicitly h as an 'any' type because type '{}' has no index signature"

Does anybody have an idea what I am missing here? Or what is the current best practice to do such an iteration with ES2015 and TypeScript (2.2.2)?

Solution

  • It contains an unknown number of objects of the same type.

    Maybe with a generic interface BigObject<T> for your dictionary?

    interface BigObject<T> {
    [index: string]: T
}

let bigObject: BigObject<object> = {}
Object.keys(bigObject).forEach(key => {
  console.log(bigObject[key])
})

    Here I wrote the type object in let bigObject: BigObject<object>. You can use a better type.