JavaScript base64解碼程式碼

下面是一段原聲javascript實現的base64解碼程式碼和大家分享一下。

程式碼如下:

[JavaScript] 純文字檢視 複製程式碼
function base64_decode(data){
  var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
  var o1, o2, o3, h1, h2, h3, h4, bits, i = 0,ac = 0,dec = "",tmp_arr = [];
  if (!data) { return data; }
  data += '';
  do {
    h1 = b64.indexOf(data.charAt(i++));
    h2 = b64.indexOf(data.charAt(i++));
    h3 = b64.indexOf(data.charAt(i++));
    h4 = b64.indexOf(data.charAt(i++));
    bits = h1 << 18 | h2 << 12 | h3 << 6 | h4;
    o1 = bits >> 16 & 0xff;
    o2 = bits >> 8 & 0xff;
    o3 = bits & 0xff;
    if (h3 == 64) {
      tmp_arr[ac++] = String.fromCharCode(o1);
    } else if (h4 == 64) {
      tmp_arr[ac++] = String.fromCharCode(o1, o2);
    } else {
      tmp_arr[ac++] = String.fromCharCode(o1, o2, o3);
    }
  } while (i < data.length);
  dec = tmp_arr.join('');
  dec = utf8_decode(dec);
  return dec;
}