"str.charCodeAt is not a function"，anybody can help me?


code is here:
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`
const fetchFile = async (file) => {
let data;

if (typeof file === "string") {
/* From base64 format */
if (/data:_data\/([a-zA-Z]*);base64,([^"]*)/.test(file)) {
data = atob(file.split(",")[1])
.split("")
.map((c) => c.charCodeAt(0));
/* From remote server/URL */
} else {
data = await (await fetch(file)).arrayBuffer();
}
} else if (file instanceof URL) {
data = await (await fetch(file)).arrayBuffer();
} else if (file instanceof File || file instanceof Blob) {
data = await readFromBlobOrFile(file);
} else {
return new Uint8Array();
}

return new Uint8Array(data);
};

createFFmpegCore().then(ffmpeg => {
const { FS } = ffmpeg;
console.log(ffmpeg);

const transcode = async () => {
await FS.writeFile('input.webm', await fetchFile('https://raw.githubusercontent.com/ffmpegwasm/testdata/master/Big_Buck_Bunny_180_10s.webm'));
await ffmpeg.exec(['-i', 'input.webm', 'output.mp4']);
const data = await FS.readFile('output.mp4');
document.getElementById('video').src = URL.createObjectURL(new Blob([data.buffer], { type: 'video/mp4' }));
}

transcode();
})
`