javascript - "Uncaught TypeError: Cannot read property 'checked' of null" -
i have problem php , javascript code.
i put simplified code here. first step, want select trip "walking" submit. got trip number 50 , shows check-box. after that, want select check-box , click "select checkbox" button. should call myfunction().
but code inside myfunction() not getting result because got error
uncaught typeerror: cannot read property 'checked' of null
and tried put myfunction() inside <head></head>, did not work well. suggestion guys?
<html> <head></head> <body> <form action = "thispage.php" method = "post"> <select name="typesselect"> <option value="">walking</option> </select> <input type="submit" name="searchformsubmit" value="search" /> </form> <button onclick="myfunction();">select checkbox</button> <?php $trip = 1; if(isset($_post['searchformsubmit'])) { $trip = 50; ?> <input type='checkbox' id="mytrip<?php echo $trip;?>"> <?php} ?> <script> function myfunction() { trips = <?php echo json_encode($trip); ?>; var array; initialize(); for(var i=0;i<trips.length;i++){ if(document.getelementbyid("mytrip"+trips[i]+"").checked){ $.get('/ajax.php?function=geodata&trip_id='+trips[i], function(data){data=json.parse(data);array=data;addline(data)}) } } } </script> </body> </html>
as @lonewolf217 mentioned in comment looking element doesn't exist.
you should similar this:
for(var i=0;i<trips.length;i++){ var elem = document.getelementbyid("mytrip"+trips[i]+""); if(elem && elem.checked){ $.get('/ajax.php?function=geodata&trip_id='+trips[i], function(data){data=json.parse(data);array=data;addline(data)}) } } whenever using getelementbyid check element returned exists before looking property.
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