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<main>
<section id="example01">
<h1>例外の伝播をわざと catch しない例</h1>
<p><button>押して開始</button></p>
<div class="console" />
</section>
<section id="example02">
<h1>例外の伝播を catch でハンドリングする例</h1>
<p><button>押して開始</button></p>
<div class="console" />
</section>
</main>
*,
*::berore,
*::after {
box-sizing: border-box;
}
h1 {
margin-top: 0;
}
main {
display: grid;
align-items: flex-start;
grid-template-columns: repeat(auto-fit, minmax(49%, 1fr));
gap: 1rem;
justify-content: center;
line-height: 1.4;
}
section {
border: 1px solid #444;
border-radius: 2rem;
padding: 2rem;
}
const failExample = document.querySelector("#example01");
const failButton = failExample.querySelector("button");
failButton.addEventListener("click", failSleep);
const failConsole = document.querySelector("#example01 .console");
/**
* 例外の伝播を無視するコード例
*/
async function failSleep(e) {
const consoleNode = clearConsole(failConsole);
createNode(consoleNode, "article", "イベントハンドラ関数を実行");
await sleep(1000);
await otherFn(consoleNode);
}
const catchExample = document.querySelector("#example02");
const catchButton = catchExample.querySelector("button");
catchButton.addEventListener("click", catchSleep);
const catchConsole = document.querySelector("#example02 .console");
/**
* 例外の伝播をハンドリングするコード例
*/
async function catchSleep(e) {
const consoleNode = clearConsole(catchConsole);
createNode(consoleNode, "article", "イベントハンドラ関数を実行");
await sleep(1000);
// ここでハンドリング!
try {
await otherFn(consoleNode);
} catch (err) {
// ハンドリング処理をここに記述
createNode(catchConsole, "p", "例外を受け取りました!");
}
}
/**
* 例外の伝播を示すために、経由させる関数
*/
async function otherFn(catchConsole) {
createNode(catchConsole, "article", "上記からさらに呼び出された関数を実行");
await sleep(1000);
return raiseExeption(catchConsole);
}
/**
* 例外を発行する関数
*/
function raiseExeption(catchConsole) {
createNode(catchConsole, "article", "例外を発行する関数を実行");
const a = "beact";
a.b.c = 1;
return a;
}
/**
* テストコード用:画面のコンソール部をクリア
*/
function clearConsole(consoleNode) {
while (consoleNode.lastChild) {
consoleNode.removeChild(consoleNode.lastChild);
// DOMツリーから取り除いたら、GCの対象にする
consoleNode.lastChild = null;
}
return consoleNode;
}
/**
* テストコード用:DOMノード生成&アペンド関数
*/
function createNode(targetNode, tagName, textContent) {
const node = document.createElement(tagName);
node.textContent = textContent;
targetNode.appendChild(node);
return targetNode;
}
/**
* テストコード用:非同期処理用のダミー関数
*/
function sleep(ms = 1000) {
return new Promise((res) => {
setTimeout(() => res(), ms);
});
}
Also see: Tab Triggers