Question

I have a button which opens a popup window and lets me to choose something from a list and then returns to parent page with the ID and NAME variables. In the parent page, I store ID in an hidden field and NAME in a textbox.
This is ok when i choose one thing from list. But now I want to choose multiple things and store ID’s and NAME’s in a listbox value and text property.
How can I do that?
These are the javascript codes I am using for textbox and hidden field.

<script type="text/javascript">
  function get_selected_machine(ID, NAME) {
      document.getElementById("txtName").value = NAME;
      document.getElementById("hdnID").value = ID;
    }
</script>

Answer 1

Below is a very simple example that illustrates how to get the values from a listbox using pure JavaScript. How you decide to store the values on the client once you have them is up to you.

HTML:

<select id="multiSelect" size="5" multiple="multiple">
    <option value="o1">Option 1</option>
    <option value="o2">Option 2</option>
    <option value="o3">Option 3</option>
    <option value="o4">Option 4</option>
    <option value="o5">Option 5</option>
    <option value="o6">Option 6</option>
</select>
<br />
<button id="btnGetValues" onclick="GetValues()">Get Values</button>

JavaScript

function GetValues() {
    //Get select object
    var myList = document.getElementById("multiSelect");

    //Create array to store selected values
    var aryMySelectOptions = new Array();

    //Loop through all values and grab selected
    for (var i = 0; i < myList.options.length; i++) {
        if (myList.options[i].selected) {
            aryMySelectOptions.push(new selectOption(myList.options[i].innerText, myList.options[i].value));
        }
    }

    //Loop through selected values and alert for debugging purposes
    for (var i = 0; i < aryMySelectOptions.length; i++) {
        alert("Text: " + aryMySelectOptions[i].text + ". Value: " + aryMySelectOptions[i].value + ".");
    }
}

function selectOption(text, value) {
    var text;
    var value;

    this.text = text;
    this.value = value;
}

Here’s a working jsFiddle.

Note: The jsFiddle uses jQuery, but only as a means of attaching to the click event of the button. I did not use jQuery for anything else because I’m assuming that you want a pure JS solutions (you didn’t tag jQuery in your post).