mirror of
https://github.com/denoland/deno.git
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b6400a25a0
Co-authored-by: Luca Casonato <hello@lcas.dev>
59 lines
1.6 KiB
JavaScript
59 lines
1.6 KiB
JavaScript
// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
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"use strict";
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((window) => {
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const illegalConstructorKey = Symbol("illegalConstructorKey");
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function requiredArguments(
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name,
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length,
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required,
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) {
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if (length < required) {
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const errMsg = `${name} requires at least ${required} argument${
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required === 1 ? "" : "s"
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}, but only ${length} present`;
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throw new TypeError(errMsg);
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}
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}
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const handlerSymbol = Symbol("eventHandlers");
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function makeWrappedHandler(handler) {
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function wrappedHandler(...args) {
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if (typeof wrappedHandler.handler !== "function") {
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return;
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}
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return wrappedHandler.handler.call(this, ...args);
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}
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wrappedHandler.handler = handler;
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return wrappedHandler;
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}
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function defineEventHandler(emitter, name, defaultValue = undefined) {
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// HTML specification section 8.1.5.1
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Object.defineProperty(emitter, `on${name}`, {
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get() {
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return this[handlerSymbol]?.get(name)?.handler ?? defaultValue;
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},
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set(value) {
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if (!this[handlerSymbol]) {
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this[handlerSymbol] = new Map();
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}
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let handlerWrapper = this[handlerSymbol]?.get(name);
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if (handlerWrapper) {
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handlerWrapper.handler = value;
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} else {
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handlerWrapper = makeWrappedHandler(value);
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this.addEventListener(name, handlerWrapper);
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}
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this[handlerSymbol].set(name, handlerWrapper);
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},
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configurable: true,
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enumerable: true,
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});
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}
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window.__bootstrap.webUtil = {
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illegalConstructorKey,
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requiredArguments,
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defineEventHandler,
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};
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})(this);
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