Target es5 when compiling JS

[jamesmoss]

This fixes #52 by targeting ES5 instead of ES6 when compiling. I've included the DOM and ES2015 libs so that types can be correctly checked.

I ran into issues with ts-jest failing tests with ES5 so I've setup a new tsconfig.test.json file which sets the target back to ES6 in the test environment.

[jharrilim]

Looks good, thank you @jamesmoss!

[jamesmoss]

@jharrilim Apologies but you're going to need to revert this as there's currently an issue which causes the lib to break when writing to the storage. Unfortunately the IE11 compatibility issue is a lot more complex than I first though.

Typescript can't handle transpiling classes which extend built in classes to ES5 (see this open issue microsoft/TypeScript#15397). As LocalStorageChanged extends CustomEvent in local-storage-events.ts this means that the ES5 version will never work properly.

Right now the only fix I can see is to get rid of LocalStorageChanged and just use CustomEvent directly. I had a go at this and got it working but my Typescript's not too hot so I'm not happy submitting a PR.

[jharrilim]

Sure, we can make a fix so that it creates an instance of CustomEvent instead of a subclass of CustomEvent.

I have just tried

export function LocalStorageChanged<TValue>(payload: LocalStorageEventPayload<TValue>) {
    return new CustomEvent('onLocalStorageChange', { detail: payload });
}
LocalStorageChanged.eventName = 'onLocalStorageChange';

and it currently generates this ES5:

function LocalStorageChanged(payload) {
    return new CustomEvent('onLocalStorageChange', { detail: payload });
}
exports.LocalStorageChanged = LocalStorageChanged;
LocalStorageChanged.eventName = 'onLocalStorageChange';

I was against it at first, but I think we should also add the CustomEvent polyfill shown here too:
https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent#Polyfill

[jharrilim]

Made an update here which no longer uses inheritance, and contains a CustomEvent polyfill:

https://github.com/rehooks/local-storage/tree/patch-67

If you have time, please try this out as well. I think it should work.

[InSuperposition]

Any update on releasing this patch?