> %parent% called `%method%` on an instance of %component%, which is no longer valid in Svelte 5. See https://svelte-5-preview.vercel.app/docs/breaking-changes#components-are-no-longer-classes for more information
## component_api_invalid_new
> Attempted to instantiate %component% with `new %name%`, which is no longer valid in Svelte 5. If this component is not under your control, set the `legacy.componentApi` compiler option to keep it working. See https://svelte-5-preview.vercel.app/docs/breaking-changes#components-are-no-longer-classes for more information
## each_key_duplicate
> Keyed each block has duplicate key at indexes %a% and %b%
@ -75,6 +75,24 @@ export function component_api_changed(parent, method, component) {
}
}
/**
*Attemptedtoinstantiate%component%with`new %name%`,whichisnolongervalidinSvelte5.Ifthiscomponentisnotunderyourcontrol,setthe`legacy.componentApi`compileroptiontokeepitworking.Seehttps://svelte-5-preview.vercel.app/docs/breaking-changes#components-are-no-longer-classes for more information
consterror=newError(`${"component_api_invalid_new"}\n${`Attempted to instantiate ${component} with \`new ${name}\`, which is no longer valid in Svelte 5. If this component is not under your control, set the \`legacy.componentApi\` compiler option to keep it working. See https://svelte-5-preview.vercel.app/docs/breaking-changes#components-are-no-longer-classes for more information`}`);
@ -115,6 +115,30 @@ Svelte provides reactive `Map`, `Set`, `Date` and `URL` classes. These can be im
<inputbind:value={url.href}/>
```
## `svelte/events`
Where possible, event handlers added with [attributes like `onclick`](/docs/event-handlers) use a technique called _event delegation_. It works by creating a single handler for each event type on the root DOM element, rather than creating a handler for each element, resulting in better performance and memory usage.
Delegated event handlers run after other event handlers. In other words, a handler added programmatically with [`addEventListener`](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener) will run _before_ a handler added declaratively with `onclick`, regardless of their relative position in the DOM ([demo](/#H4sIAAAAAAAAE41Sy2rDMBD8lUUXJxDiu-sYeugt_YK6h8RaN6LyykgrQzH6965shxJooQc_RhrNzA6aVW8sBlW9zYouA6pKPY-jOij-GjMIE1pGwcFF3-WVOnTejNy01LIZRucZZnD06iIxJOi9G6BYjxVPmZQfiwzaTBkL2ti73R5ODcwLiftIHRtHcLuQtuhlc9tpuSyBbyZAuLloNfhIELBzpO8E-Q_O4tG6j13hIqO_y0BvPOpiv0bhtJ1Y3pLoeNH6ZULiswmMJLZFZ033WRzuAvstdMseOXqCh9SriMfBTfgPnZxg-aYM6_KnS6pFCK6GdJVHPc0C01JyfY0slUnHi-JpfgjwSzUycdgmfOjFEP3RS1qdhJ8dYMDFt1yNmxxU0jRyCwanTW9Qq4p9xPSevgHI3m43QAIAAA==)). It also means that calling `event.stopPropagation()` inside a declarative handler _won't_ prevent the programmatic handler (created inside an action, for example) from running.
To preserve the relative order, use `on` rather than `addEventListener` ([demo](/#H4sIAAAAAAAAE3VRy26DMBD8lZUvECkqdwpI_YB-QdJDgpfGqlkjex2pQv73rnmoStQeMB52dnZmmdVgLAZVn2ZFlxFVrd6mSR0Vf08ZhDtaRsHBRd_nL03ovZm4O9OZzTg5zzCDo3cXiSHB4N0IxdpWvD6RnuoV3pE4rLT8WGTQ5p6xoE20LA_QdjAvJB4i9WxE6nYhbdFLcaucuaqAbyZAuLloNfhIELB3pHeC3IOz-GLdZ1m4yOh3GRiMR10cViucto7l9MjRk9gvxdsRit6a_qs47q1rT8qvpvpdDjXChqshXWdT7SwwLVtrrpElnAguSu38EPCPEOItbF4eEhiifxKkdZLw8wQYcZlbrYO7bFTcdPJbR6fNYFCrmn3E9JF-AJZOg9MRAgAA)):
```js
// @filename: index.ts
const element: Element = null as any;
// ---cut---
import { on } from 'svelte/events';
const off = on(element, 'click', () => {
console.log('element was clicked');
});
// later, if we need to remove the event listener:
off();
```
`on` also accepts an optional fourth argument which matches the options argument for `addEventListener`.
If this component is not under your control, you can use the `legacy.componentApi` compiler option for auto-applied backwards compatibility (note that this adds a bit of overhead to each component). This will also add `$set` and `$on` methods for all component instances you get through `bind:this`.
If this component is not under your control, you can use the `legacy.componentApi` compiler option for auto-applied backwards compatibility, which means code using `new Component(...)` keeps working without adjustments (note that this adds a bit of overhead to each component). This will also add `$set` and `$on` methods for all component instances you get through `bind:this`.
Rich Harris
2 years ago