to Select / Deselect all Checkboxes using jQuery

*****************************JS********************************************
$(document).ready(function() {
    $('#selecctall').click(function(event) {  //on click
        if(this.checked) { // check select status
            $('.checkbox1').each(function() { //loop through each checkbox
                this.checked = true;  //select all checkboxes with class "checkbox1"            
            });
        }else{
            $('.checkbox1').each(function() { //loop through each checkbox
                this.checked = false; //deselect all checkboxes with class "checkbox1"                    
            });      
        }
    });
 
});

**********************html********************************************
 Check/Uncheck All        
<input    type="checkbox" name="cat[]" id="selectall">
               Architecture and Design  <input  class="checkbox1"  type="checkbox" name="cat[]" value="1">
               Builders/Contractors      <input  class="checkbox1"  type="checkbox" name="cat[]" value="2">
                Building Material        <input  class="checkbox1" type="checkbox" name="cat[]" value="3">
               Construction Equipments   <input class="checkbox1"   type="checkbox" name="cat[]" value="4">
                Doors and Windows  <input  class="checkbox1"  type="checkbox" name="cat[]" value="5">
                Flooring and Furnishes    <input  class="checkbox1"  type="checkbox" name="cat[]" value="7">
               Green Technology      <input   class="checkbox1" type="checkbox" name="cat[]" value="8">
                Mechanical & Electrical  <input class="checkbox1"   type="checkbox" name="cat[]" value="9">
               Safety Equipment   <input  class="checkbox1"  type="checkbox" name="cat[]" value="10">