Question

I have this script in my < head > :

<script>
var rad = document.getElementsByName('search_type');
alert(rad[1]);
var prev = null;
for (var i = 0; i < rad.length; i++) {
    rad[i].onclick = function() {
        (prev)? console.log(prev.value):null;
        if(this !== prev) {
            prev = this;
        }
        console.log(this.value)
        alert(this.value);
    };
}
</script>

and this is my form:

<form name="search_form" action="<?php echo $_SERVER['PHP_SELF']?>" method="post"> 
    <table border="0"> 
        <tr>
            <td class="input">
                <input type="radio" name="search_type" value="search_code" checked>1st type<br>
                <input type="radio" name="search_type" value="search_title">2nd type<br>
                <input type="radio" name="search_type" value="search_filter">3rd type<br>
            </td>
        <tr/>
    </table> 
</form>

but none of alerts work. I have no error in console. please help.

Answer 1

You are running the script before the HTML code for the radio buttons has been parsed.

Place the script below the form, or run the code in the load event:

window.onload = function() {

  var rad = document.getElementsByName('search_type');
  alert(rad[1]);
  var prev = null;
  for (var i = 0; i < rad.length; i++) {
    rad[i].onclick = function() {
      (prev)? console.log(prev.value):null;
      if(this !== prev) {
        prev = this;
      }
      console.log(this.value)
      alert(this.value);
    };
  }

};