Select multiple values in a multiple select box with Jquery

Question

So I have two multiple select boxes like this

<select id="foo" multiple="multiple">
    <option value="1">Option 1</option>
    <option value="2">Option 2</option>
</select>

<select id="bar" multiple="multiple">
    <option value="1">Opt 1</option>
    <option value="2">Opt 2</option>
    <option value="3">Opt 3</option>
    <option value="4">Opt 4</option>
</select>
<a href="#" onclick="select()">Select</a>

What I'm trying to do is that when 'Select' is clicked, any option in "#bar" that has the same value with an option in "#foo" would be selected. In this case Opt 1 and Opt 2 in "#bar" should be selected. I've no idea why my javascript won't work. I know it must be something very simple. I just can't see it. :( So my Javascript function is as followed:

function select(){
    var vals = new Array();
    var iter = 0;
    $("#foo option").each(function(){
        var v = $(this).val();
        $('#bar option').each(function(){
            if ($(this).val() == v)
            {
                vals[iter] = v;
                iter++;
                break;
            }
        });
    });
    $("#bar").val(vals);
 }

Scoliosis

Answer 1

UPDATE after seeing KON's example

DEMO

$("#sel").click(function(e) {
  e.preventDefault(); // cancel the link itself
  $("#bar").val($("#foo").val());
});

---

<a href="#" id="sel">Select</a>

---

Older example using each

DEMO

$("#sel").click(function(e) { // when link clicked
  e.preventDefault();
  $("#foo option:selected ").each(function(){
    var v = $(this).attr("value"); // first select's value
    $('#bar option').each(function(){
      if ($(this).attr("value") == v) { 
        $(this).attr("selected",true); // select if same value
      }
    });
  });
})

Lagging

Answer 2

Check this out http://jsfiddle.net/NtF8J/

html

<select multiple>
    <option value="1">Option 1</option>
    <option value="2">Option 2</option>
    <option value="3">Option 3</option>
    <option value="4">Option 4</option>
</select>

<select multiple>
    <option value="1">Option 1</option>
    <option value="2">Option 2</option>
    <option value="3">Option 3</option>
    <option value="4">Option 4</option>
</select>

<button> random </button>​

jquery

$(function(){
  $(document.body).delegate(
    'select:first', 'change', function(){
      $('select:not(:first)').val(
        $(this).val()
      )
    }
  )
  .delegate(
    'button', 'click', function(){
     $('select').val([1,2,3,4].filter(function(){return!!Math.round(Math.random() * 1)}))
    }
  )
});



​

Gardel

When posting your answers make sure you include your code. Fiddle's don't last forever and the goal of SO is to create a lasting repository of good questions with good answers. Links die. We want others to benefit from your knowledge. – Smallminded

Apologies, didn't know they don't last forever. – Gardel

No problem. I edited your question for you to include the code. +1 for a nicely coded answer. – Smallminded

The asker is new at JS - I do not think your random selection generator with filter on hardcoded values is very explanatory or even answers the question. Why delegate by the way? – Lagging

Still thanks for teaching me that jQuery can select multiple using just val – Lagging