JS全角转半角

<input type="button" onclick="changeHalf();" value="全转半" />

changeHalf = function(){

//得到fck文本编辑器内容
var str = FCKeditorAPI.GetInstance("text").EditorDocument.body.innerText; 
var tmp = ""; 
for(var i=0;i<str.length;i++){ 
if(str.charCodeAt(i)>65248&&str.charCodeAt(i)<65375){ 
tmp += String.fromCharCode(str.charCodeAt(i)-65248); 
}else{ 
tmp += String.fromCharCode(str.charCodeAt(i)); 
} 
} 
FCKeditorAPI.GetInstance("text").EditorDocument.body.innerText = tmp;
}