ArrayBuffer concat

<!doctype html>
<script src="https://zh.js.cx/test/libs.js"></script>
<script src="test.js"></script>
<script>

  function concat(arrays) {
    const arr = arrays.reduce((pre, cur) => {
      return pre.concat(Array.from(cur))
    }, [])
    return new Uint8Array(arr)
  }
  
  let chunks = [
    new Uint8Array([0, 1, 2]),
    new Uint8Array([3, 4, 5]),
    new Uint8Array([6, 7, 8])
  ];
  
  console.log(Array.from(concat(chunks))); // 0, 1, 2, 3, 4, 5, 6, 7, 8
  
  console.log(concat(chunks).constructor.name); // Uint8Array

</script>

</html>

describe("concat", function() {
  let chunks = [
    new Uint8Array([0, 1, 2]),
    new Uint8Array([3, 4, 5]),
    new Uint8Array([6, 7, 8])
  ];

  it("result has the same array type", function() {

    let result = concat(chunks);

    assert.equal(result.constructor, Uint8Array);
  });

  it("concatenates arrays", function() {

    let result = concat(chunks);

    assert.deepEqual(result, new Uint8Array([0, 1, 2, 3, 4, 5, 6, 7, 8]));

  });

  it("returns empty array on empty input", function() {

    let result = concat([]);

    assert.equal(result.length, 0);

  });

});