what went wrong with parseInt

Question

i just encounter 1 problem on the parseInt i do apply this parseInt for all my project but today i just encounter this

i have a normal text input <input type='text' name='KG'> and i using jquery to retrieve the input value, then write into another input <input type='text' name='KG2'>

below are my jquery code

$(":input[name='KG']").keyup(calc);
function calc(){
   var kg = $(":input[name='KG']").val();
   kg=parseInt(kg);
   $(":input[name='KG2']").val(kg);
}

guess what, this the result i get
input@KG   >   show@KG2
28   >   28
028   >   2
34   >   34
034   >   28
9   >   9
09   >   0

anyone know what went wrong? it can be solve by using Math.round.

Answer 1

028, 034 and 09 are being treated as octal numbers because they start with 0 and you didn't specify a base. 8 and 9 are invalid digits, so you get 2 and 0 for the first and last, and the second one is converted to decimal 3*8 + 4 = 28.

Use parseInt(kg,10);