arrayBuffer 轉base64

var buffer = new ArrayBuffer(8);// buffer 是接收到後臺的流
function _arrayBufferToBase64( buffer ) {
    var binary = '';
    var bytes = new Uint8Array( buffer );
    var len = bytes.byteLength;
    for (var i = 0; i < len; i++) {
        binary += String.fromCharCode( bytes[ i ] );
    }
    return 'data:application/pdf;base64,'+ window.btoa( binary );
}


若是是圖片類型，能夠拼接 data:image/jpeg;base64,或data:image/png;base64,