HTML5 Blob與ArrayBuffer、TypeArray和字元串String之間轉換

1.將String字元串轉換成Blob對象

//將字元串 轉換成 Blob 對象
var blob = new Blob(["Hello World!"], {
    type: 'text/plain'
});
console.info(blob);
console.info(blob.slice(1, 3, 'text/plain'));

2.將TypeArray  轉換成 Blob 對象

//將 TypeArray  轉換成 Blob 對象
var array = new Uint16Array([97, 32, 72, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100, 33]);
//測試成功
//var blob = new Blob([array], { type: "application/octet-binary" });
//測試成功， 註意必須[]的包裹
var blob = new Blob([array]);
//將 Blob對象 讀成字元串
var reader = new FileReader();
reader.readAsText(blob, 'utf-8');
reader.onload = function (e) {
    console.info(reader.result); //a Hello world!
}

ArrayBuffer轉Blob

var buffer = new ArrayBuffer(32);
var blob = new Blob([buffer]);       // 註意必須包裹[]

3，將Blob對象轉換成String字元串，使用FileReader的readAsText方法

//將字元串轉換成 Blob對象
var blob = new Blob(['中文字元串'], {
    type: 'text/plain'
});
//將Blob 對象轉換成字元串
var reader = new FileReader();
reader.readAsText(blob, 'utf-8');
reader.onload = function (e) {
    console.info(reader.result);
}

4.將Blob對象轉換成ArrayBuffer，使用FileReader的 readAsArrayBuffer方法

//將字元串轉換成 Blob對象
var blob = new Blob(['中文字元串'], {
    type: 'text/plain'
});
//將Blob 對象轉換成 ArrayBuffer
var reader = new FileReader();
reader.readAsArrayBuffer(blob);
reader.onload = function (e) {
    console.info(reader.result); //ArrayBuffer {}
    //經常會遇到的異常 Uncaught RangeError: byte length of Int16Array should be a multiple of 2
    //var buf = new int16array(reader.result);
    //console.info(buf);

    //將 ArrayBufferView  轉換成Blob
    var buf = new Uint8Array(reader.result);
    console.info(buf); //[228, 184, 173, 230, 150, 135, 229, 173, 151, 231, 172, 166, 228, 184, 178]
    reader.readAsText(new Blob([buf]), 'utf-8');
    reader.onload = function () {
        console.info(reader.result); //中文字元串
    };

    //將 ArrayBufferView  轉換成Blob
    var buf = new DataView(reader.result);
    console.info(buf); //DataView {}
    reader.readAsText(new Blob([buf]), 'utf-8');
    reader.onload = function () {
        console.info(reader.result); //中文字元串
    };
}