<!-- html部分 -->
<a id="h">點(diǎn)此進(jìn)行下載</a>
<!-- js部分 -->
<script>
  var blob = new Blob(["Hello World"]);
  var url = window.URL.createObjectURL(blob);
  var a = document.getElementById("h");
  a.download = "helloworld.txt";
  a.href = url;
</script>

<!-- html部分 -->
<input type="file" id='f' />
<img id='img' style="width: 200px;height:200px;" />
<!-- js部分 -->
<script>
  document.getElementById('f').addEventListener('change', function (e) {
    var file = this.files[0];
    const img = document.getElementById('img');
    const url = window.URL.createObjectURL(file);
    img.src = url;
    img.onload = function () {
        // 釋放一個(gè)之前通過調(diào)用 URL.createObjectURL創(chuàng)建的 URL 對(duì)象
        window.URL.revokeObjectURL(url);
    }
  }, false);
</script>

<!-- html部分 -->
<input type="file" id='f' />
<!-- js部分 -->
<script>
  function upload(blob) {
    var xhr = new XMLHttpRequest();
    xhr.open('POST', '/ajax', true);
    xhr.setRequestHeader('Content-Type', 'text/plain')
    xhr.send(blob);
  }
  document.getElementById('f').addEventListener('change', function (e) {
    var blob = this.files[0];
    const CHUNK_SIZE = 20; .
    const SIZE = blob.size;
    var start = 0;
    var end = CHUNK_SIZE;
    while (start < SIZE) {
        upload(blob.slice(start, end));
        start = end;
        end = start + CHUNK_SIZE;
    }
  }, false);
</script>

app.use(async (ctx, next) => {
    await next();
    if (ctx.path === '/ajax') {
        const req = ctx.req;
        const body = await parse(req);
        ctx.status = 200;
        console.log(body);
        console.log('---------------');
    }
});

<input type="file" id='f' />


document.getElementById('f').addEventListener('change', function (e) {
    var file = this.files[0];
    const reader = new FileReader();
    reader.onload = function () {
        const content = reader.result;
        console.log(content);
    }
    reader.readAsText(file);
}, false); 

document.getElementById('f').addEventListener('change', function (e) {
  const file = this.files[0];
  const fileReader = new FileReader();
  fileReader.onload = function () {
    const result = fileReader.result;
    console.log(result)
  }
  fileReader.readAsArrayBuffer(file);
}, false);

const xhr = new XMLHttpRequest();
xhr.open("GET", "ajax", true);
xhr.responseType = "arraybuffer";
xhr.onload = function () {
    console.log(xhr.response)
}
xhr.send();

const app = new Koa();
app.use(async (ctx) => {
  if (pathname = '/ajax') {
        ctx.body = 'hello world';
        ctx.status = 200;
   }
}).listen(3000)

const typedArray1 = new Int8Array(8);
typedArray1[0] = 32;

const typedArray2 = new Int8Array(typedArray1);
typedArray2[1] = 42;
 
console.log(typedArray1);
//  output: Int8Array [32, 0, 0, 0, 0, 0, 0, 0]
 
console.log(typedArray2);
//  output: Int8Array [32, 42, 0, 0, 0, 0, 0, 0]

const buffer = new ArrayBuffer(16);
const view = new DataView(buffer);
view.setInt8(2, 42);
console.log(view.getInt8(2));
// 輸出: 42

const app = new Koa();
app.use(async (ctx, next) => {
    if (ctx.path === '/ajax') {
        const chunks = [];
        const req = ctx.req;
        req.on('data', buf => {
            chunks.push(buf);
        })
        req.on('end', () => {
            let buffer = Buffer.concat(chunks);
            console.log(buffer.toString())
        })
    }
});
app.listen(3000)

const xhr = new XMLHttpRequest();
xhr.open("POST", "ajax", true);
xhr.setRequestHeader('Content-Type', 'text/plain')
xhr.send("asdasdsadfsdfsadasdas");