Why am I not getting the value from onChange with Select?

问题

Testing part of a form. So, right now I just want to alert what the user selects:

JS:

function getData(title)
{
     alert(title);
}

HTML generated by PHP:

<select name="currentList" onChange="getData(this);">
     <option value="hat">Hat</option>
     <option value="shirt">Shirt</option>
     <option value="pants">Pants</option>
</select>

when I change the value I get an alert with:

[object HTMLSelectElement]

回答1:

try alert(this.value)

回答2:

With this you're passing the HTML select element to the function, not the value of the selected option. To obtain the value of the selected option, you need to get the selected option from the options by selectedIndex and then get its value. In a nutshell:

function getData(dropdown) {
    var value = dropdown.options[dropdown.selectedIndex].value;
    alert(value);
}

回答3:

With jQuery, you could be concise with alert($("#currentList").val());, as long as you add the id="currentList" to the select list. This way you don't have to pass "this" to the onchange function.

回答4:

You can try

alert(title.value)

来源：https://stackoverflow.com/questions/3597456/why-am-i-not-getting-the-value-from-onchange-with-select