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document.getElementById("cbox0").checked = true;

I am using this statement to auto check a checkbox but i get TypeError: Cannot set property 'checked' of null for CheckBox this error. I have tried to use if statement to check if its not a null but it also give me the same error. 

jsp+='<input id="cbox'+index+'" type="checkbox" name="pare" value="'+rightCard.oid+'" onchange="myFunction('+index+')"><label for="cboxCard'+index+'">&nbsp;</label>';

document.getElementById("cbox0").checked = true;

I am using this statement to auto check a checkbox but i get TypeError: Cannot set property 'checked' of null for CheckBox this error. I have tried to use if statement to check if its not a null but it also give me the same error. 

jsp+='<input id="cbox'+index+'" type="checkbox" name="pare" value="'+rightCard.oid+'" onchange="myFunction('+index+')"><label for="cboxCard'+index+'">&nbsp;</label>';
  • javascript
  • checkbox
Share Improve this question asked Aug 25, 2017 at 2:55 kuhandran samudra pandiyankuhandran samudra pandiyan 731 gold badge2 silver badges9 bronze badges
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2 Answers 2

Reset to default 4

There could be 2 possible problems.

  1. There is no checkbox with the id as cbox0. Hence, getElementById returns null, leading to your error
  2. Your JavaScript is executed before your checkbox is loaded into the DOM. You can solve this by wrapping your code inside a DOMContentLoaded event listener, like this

document.addEventListener("DOMContentLoaded", function() {
  document.getElementById("cbox0").checked = true;
});
<input id="cbox0" type="checkbox" name="pare" value="test">

Note that the snippet above works even without the event listener on StackOverflow. That's probably because StackOverflow's snippet runs it's JavaScript similar to what I've written.

wrap your code within an onload event.

本文标签： javascriptTypeError Cannot set property 39checked39 of null for CheckBoxStack Overflow

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