js checkbox selects all and puts the obtained value into the input_form effects

<meta http-equiv="Content-Type" content="text/html; charset=gb2312"> <title>Untitled Document</title> <form id="form1" name="form1" method="post" action=""> <input type="checkbox" name="1001" id="1001" value="1001" onclick="checkAll(this,'mk1001','1001')" checked> <label for="1000"> </label>Check 1<input name="mk1001" type="checkbox" id="mk1001" value="1" checked> <input name="mk1001" type="checkbox" id="mk" value="2" checked> <input name="mk1001" type="checkbox" id="mk2" value="3" checked> <input name="mk1001" type="checkbox" id="mk3" value="4" checked> <input name="mk1001" type="checkbox" id="mk4" value="5" checked> <input name="mk1001" type="checkbox" id="mk5" value="6" checked> <input name="mk1001" type="checkbox" id="mk6" value="7" checked> <br> <input type="checkbox" name="1002" id="1002" value="1002" onclick="checkAll(this,'mk1002','1002')"> <label for="1002"> </label>Check 2<input name="mk1002" type="checkbox" id="mk7" value="1"> <input name="mk1002" type="checkbox" id="mk8" value="2"> <input name="mk1002" type="checkbox" id="mk9" value="3"> <input name="mk1002" type="checkbox" id="mk10" value="4"> <input name="mk1002" type="checkbox" id="mk11" value="5"> <input name="mk1002" type="checkbox" id="mk12" value="6"> <input name="mk1002" type="checkbox" id="mk13" value="7"> <br> <input type="checkbox" name="1003" id="1003" value="1003" onclick="checkAll(this,'mk1003','1003')"> <label for="1003"> </label>Check 3<input name="mk1003" type="checkbox" id="mk14" value="1"> <input name="mk1003" type="checkbox" id="mk15" value="2"> <input name="mk1003" type="checkbox" id="mk16" value="3"> <input name="mk1003" type="checkbox" id="mk17" value="4"> <input name="mk1003" type="checkbox" id="mk18" value="5"> <input name="mk1003" type="checkbox" id="mk19" value="6"> <input name="mk1003" type="checkbox" id="mk20" value="7"> <br> <input type="checkbox" name="1004" id="1004" value="1004" onclick="checkAll(this,'mk1004','1004')"> <label for="1004"> </label>Check 4<input name="mk1004" type="checkbox" id="mk21" value="1"> <input name="mk1004" type="checkbox" id="mk22" value="2"> <input name="mk1004" type="checkbox" id="mk23" value="3"> <input name="mk1004" type="checkbox" id="mk24" value="4"> <input name="mk1004" type="checkbox" id="mk25" value="5"> <input name="mk1004" type="checkbox" id="mk26" value="6"> <input name="mk1004" type="checkbox" id="mk27" value="7"> <br> <br> Please pass the values </form>