Move cursor to next field with Javascript

Basically the function below is a listener for a change in selection of one dropdown. I want the cursor to move to the next field on the page as well the below function is executed. How do I do this in Javascript? The next field on the page is an ExtJs textbox.

function changeVehicleCondition() {
        var ValuationSource = getCurrentValuationSource();
        var vehicleConditionId = vehiclePnl.VehicleConditions.getValue();

        if (ValuationSource == 0) {
            vehiclePnl.VehicleConditionId.setValue(0);
        } else {
            vehiclePnl.VehicleConditionId.setValue(vehicleConditionId);
        }
    }

Edi开发者_运维技巧t: focus() doesn't work for me, because I tried this already:

vehiclePnl.Mileage.focus();

with no luck..

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For ExtJs you apparentley have to do this:

focus( true, false );

true tells it to select the text in the next field and false tells it whether or not to delay. it actually didn't work for me but i think thats because my controls don't match up, but that's the code to do it.

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This is with no knowledge of extjs

<select id="listen">...</select>
<input id="focus" />
<script type="text/javascript">
document.getElementById('listen').onchange = function () {
    changeVehicleCondition()
    document.getElementById('focus').focus()
}
</script>

The script tag can be anywhere after the select. You can also do it this way:

<select id="listen" onchange="changeVehicleCondition(); document.getElementById('focus').focus()">...</select>
<input id="focus" />

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Lets say your form panel is defined as variable "vehiclePnl" and the next field your wanted to focused is have name attribute "Mileage". Instead using your previous code

vehiclePnl.Mileage.focus();

Then you should use this code bellow

vehiclePnl.getForm().findField("Mileage").focus();