textarea byte check

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01.function textAreaLengthCheck(thisObj, maxLengthByte) {

02.    var tempByteLength = 0, cutByteLength = 0;

03.    for(var i = 0; i < thisObj.value.length; i++) {

04.        if(escape(thisObj.value.charAt(i)).length > 4) {

05.            tempByteLength += 2;

06.        } else {

07.            tempByteLength++;

08.        }

09. 

10. 

11. 

12.        if(tempByteLength < maxLengthByte) {

13.            cutByteLength++;

14.        }

15.    }

16.    if(tempByteLength > maxLengthByte) {

17.        alert("max byte : " + maxLengthByte);

18.        thisObj.value = thisObj.value.substring(0, (cutByteLength%2==1)?cutByteLength:cutByteLength+1);

19.    }

20. 

21.}

<textarea onkeyup="textAreaLengthCheck(this, 10)" name="test"></textarea>
ex.