Handle errors according to Web IDL conventions

[zolkis]

When handling errors, the spec should follow the Web IDL convention:

Simple exceptions can be created by providing their error name. A DOMException can be created by providing its error name followed by DOMException. Exceptions can also be thrown, by providing the same details required to create one.

[anssiko]

Thanks for filing this.

We should align both the simple exceptions and DOMException usage with conventions. Here's my understanding:

Simple exceptions are created with a "new" keyword because they're ECMAScript error types. IOW, in JS console this test should be true: typeof new TypeError === 'object'.

To create a new DOMException with any of these names we don't use the "new" keyword but the "newly created" syntax:

To create a new DOMException with error name "SyntaxError":
Let object be a newly created "SyntaxError" DOMException.

Please investigate that my understanding is correct and once you're confident apply the conventions to the whole spec.

[zolkis]

The spec prose to be used, as also done in html, infra, fetch etc. specs:

1. For simple exceptions,

throw a {{TypeError}}

or

reject |promise| with a {{TypeError}}

2. For DOMExceptions,

throw a "{{SecurityError}}" {{DOMException}}

or

reject |promise| with a "{{SecurityError}}" {{DOMException}}

[anssiko]

Thanks for checking the other specs too, that looks right to me.