js odd and even number judgment code_javascript skills

There are two variables a and b
If a=1,3,5,7,9 then b="odd number"
If a=2,4,6,8 then b="even number"
If a="0" then b="zero"

<form name="abc"> <input name="num" id="num" type="text" value=""> <input name="chk" id="chk" type="button" value="检查" onclick="show(this.form.num.value)"> </form>
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