javascript 函式 將全型轉半型

function Asc(obj)
{
var text = obj.value;

var asciiTable = "!\"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~";
var big5Table = "%uFF01%u201D%uFF03%uFF04%uFF05%uFF06%u2019%uFF08%uFF09%uFF0A%uFF0B%uFF0C%uFF0D%uFF0E%uFF0F%uFF10%uFF11%uFF12%uFF13%uFF14%uFF15%uFF16%uFF17%uFF18%uFF19%uFF1A%uFF1B%uFF1C%uFF1D%uFF1E%uFF1F%uFF20%uFF21%uFF22%uFF23%uFF24%uFF25%uFF26%uFF27%uFF28%uFF29%uFF2A%uFF2B%uFF2C%uFF2D%uFF2E%uFF2F%uFF30%uFF31%uFF32%uFF33%uFF34%uFF35%uFF36%uFF37%uFF38%uFF39%uFF3A%uFF3B%uFF3C%uFF3D%uFF3E%uFF3F%u2018%uFF41%uFF42%uFF43%uFF44%uFF45%uFF46%uFF47%uFF48%uFF49%uFF4A%uFF4B%uFF4C%uFF4D%uFF4E%uFF4F%uFF50%uFF51%uFF52%uFF53%uFF54%uFF55%uFF56%uFF57%uFF58%uFF59%uFF5A%uFF5B%uFF5C%uFF5D%uFF5E";

var result = "";
for (var i = 0; i < text.length; i++) {
var val = escape(text.charAt(i));
var j = big5Table.indexOf(val);
result += (((j > -1) && (val.length == 6)) ? asciiTable.charAt(j / 6) : text.charAt(i));
}

obj.value = result;

}