Check out example codes for "html radio button checked". It will help you in understanding the concepts better.

Code Example 1

function check(id) {
  document.getElementById(id).checked = true;
}

Code Example 2

<input type="radio" name="imgsel" value="" checked>

Code Example 3

checked="checked"

Code Example 4

//checked
  <input type="radio" id="huey" name="drone" value="huey"
         checked>

Code Example 5

<input type="radio" id="male" name="gender" value="male">
<label for="male">Male</label><br>
<input type="radio" id="female" name="gender" value="female">
<label for="female">Female</label><br>
<input type="radio" id="other" name="gender" value="other">
<label for="other">Other</label>

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