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// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
"use strict";
((window) => {
const illegalConstructorKey = Symbol("illegalConstructorKey");
function requiredArguments(
name,
length,
required,
) {
if (length < required) {
const errMsg = `${name} requires at least ${required} argument${
required === 1 ? "" : "s"
}, but only ${length} present`;
throw new TypeError(errMsg);
}
}
const handlerSymbol = Symbol("eventHandlers");
function makeWrappedHandler(handler) {
function wrappedHandler(...args) {
if (typeof wrappedHandler.handler !== "function") {
return;
}
return wrappedHandler.handler.call(this, ...args);
}
wrappedHandler.handler = handler;
return wrappedHandler;
}
function defineEventHandler(emitter, name, defaultValue = undefined) {
// HTML specification section 8.1.5.1
Object.defineProperty(emitter, `on${name}`, {
get() {
return this[handlerSymbol]?.get(name)?.handler ?? defaultValue;
},
set(value) {
if (!this[handlerSymbol]) {
this[handlerSymbol] = new Map();
}
let handlerWrapper = this[handlerSymbol]?.get(name);
if (handlerWrapper) {
handlerWrapper.handler = value;
} else {
handlerWrapper = makeWrappedHandler(value);
this.addEventListener(name, handlerWrapper);
}
this[handlerSymbol].set(name, handlerWrapper);
},
configurable: true,
enumerable: true,
});
}
window.__bootstrap.webUtil = {
illegalConstructorKey,
requiredArguments,
defineEventHandler,
};
})(this);
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