57 lines
2.3 KiB
JavaScript
57 lines
2.3 KiB
JavaScript
import { directive, PartType } from '../directive.js';
|
|
import { AsyncReplaceDirective } from './async-replace.js';
|
|
import { clearPart, insertPart, setChildPartValue } from '../directive-helpers.js';
|
|
|
|
/**
|
|
* @license
|
|
* Copyright 2017 Google LLC
|
|
* SPDX-License-Identifier: BSD-3-Clause
|
|
*/
|
|
class AsyncAppendDirective extends AsyncReplaceDirective {
|
|
// Override AsyncReplace to narrow the allowed part type to ChildPart only
|
|
constructor(partInfo) {
|
|
super(partInfo);
|
|
if (partInfo.type !== PartType.CHILD) {
|
|
throw new Error('asyncAppend can only be used in child expressions');
|
|
}
|
|
}
|
|
// Override AsyncReplace to save the part since we need to append into it
|
|
update(part, params) {
|
|
this.__childPart = part;
|
|
return super.update(part, params);
|
|
}
|
|
// Override AsyncReplace to append rather than replace
|
|
commitValue(value, index) {
|
|
// When we get the first value, clear the part. This lets the
|
|
// previous value display until we can replace it.
|
|
if (index === 0) {
|
|
clearPart(this.__childPart);
|
|
}
|
|
// Create and insert a new part and set its value to the next value
|
|
const newPart = insertPart(this.__childPart);
|
|
setChildPartValue(newPart, value);
|
|
}
|
|
}
|
|
/**
|
|
* A directive that renders the items of an async iterable[1], appending new
|
|
* values after previous values, similar to the built-in support for iterables.
|
|
* This directive is usable only in child expressions.
|
|
*
|
|
* Async iterables are objects with a [Symbol.asyncIterator] method, which
|
|
* returns an iterator who's `next()` method returns a Promise. When a new
|
|
* value is available, the Promise resolves and the value is appended to the
|
|
* Part controlled by the directive. If another value other than this
|
|
* directive has been set on the Part, the iterable will no longer be listened
|
|
* to and new values won't be written to the Part.
|
|
*
|
|
* [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for-await...of
|
|
*
|
|
* @param value An async iterable
|
|
* @param mapper An optional function that maps from (value, index) to another
|
|
* value. Useful for generating templates for each item in the iterable.
|
|
*/
|
|
const asyncAppend = directive(AsyncAppendDirective);
|
|
|
|
export { asyncAppend };
|
|
//# sourceMappingURL=async-append.js.map
|