For of & Map そして Async & Await

Posted on by IKIX_wbdv

　ECMAScriptの仕様改定に伴うJavaScriptの新しい文法．var句，function句，配列表示を使わなくなれる代わりに，const/let句，アロー演算子，for of句を使う．また，async/await句が導入され，非同期処理が簡単にできる．

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>Demo - For of</title>
    <script>
	const i = [10, 20, 30];
	const for_of = async () => {
	    for(let v of i){
		await document.writeln(v);
	    }
	}
	const map_for_of = async () => {
	    const m = new Map([
		['A', 'K'],
		['J', 'Q']
	    ]);
	    for(let [k, v] of m){
		await document.writeln(`${k} : ${v}`);
	    }
	}
	</script>
</head>
<body>
    <button onclick="for_of()">For of</button>
    <button onclick="map_for_of()">Map</button>
    <button onclick="for_of(); map_for_of()">Async</button>
</body>
</html>