Setting value to textbox at client side not showing that value in Safari

// JavaScript
function ChangeTextBox(textbox)
    {
        var prefix = textbox.id.substring(0,textbox.id.lastIndexOf("_") + 1);
        var ProductList = document.getElementById(prefix +  'HiddenProduct').value.split(";;");
        var selected;
        //MBT Phase2-Release1-LUW1
        //Begin:Kunal April-2014
        //Product selection is not working for Non-IE Browser
        if (navigator.appVersion.indexOf("MSIE") != -1) 
        {
            for(var i = 0; i < document.getElementById(prefix + 'rbgProduct').childNodes[0].childNodes.length; i++)
            {
                if(document.getElementById(prefix + 'rbgProduct_' + i).checked == true)
                {
                    textbox.value = ProductList[i];
                    selected = i;
                }
            }
        }
        else
        {
       
         for(var i = 0; i < ProductList.length-1; i++)
            {
                if(document.getElementById(prefix + 'rbgProduct_' + i).checked == true)
                {
                    $(textbox)[0].textContent = ProductList[i];
                    $(textbox)[0].innerText = ProductList[i];
                    $(textbox)[0].value = ProductList[i];
                    selected = i;
                }
            }

        }

// Server Side
public override void RenderControl(HtmlTextWriter writer)
        {
            rbgProduct.Attributes.Add("onclick", "ChangeTextBox(" + txtProductDescription.ClientID + ")");
            
            txtProductDescription.Attributes.Add("readonly", "readonly");
            base.RenderControl(writer);
        }