<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title>DATA URI 変換</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<body>
<input type="file" id="fileform">
<br>
<br>
<textarea id="datauri" cols="100" rows="30"></textarea>
<br>
<button type="button" id="copybutton">コピー</button>
<script>
const toBase64DataUri = file => new Promise(resolve => {
const reader = new FileReader();
reader.onload = () => resolve(reader.result);
reader.readAsDataURL(file);
});
document.getElementById("fileform").addEventListener("input", async (e) => {
const file = e.target.files[0];
const datauri = await toBase64DataUri(file);
document.getElementById("datauri").value = datauri;
}, false);
document.getElementById("copybutton").addEventListener("click", () => {
document.getElementById("datauri").select();
document.execCommand("copy");
}, false);
</script>
</body>
</html>
