你可以这样做:
HTML
<form method="POST">
<img src="german.png" onclick="switchCountry(this);"/>
<input id="country" name="country" type="hidden" value="german" />
<input type="submit" value="Submit" />
</form>
JavaScript
var countries = ['german', 'netherlands', 'swiss'];
var switchCountry = function(img) {
var input = document.getElementById('country'),
oldValue = input.getAttribute('value'),
newValue = countries[(countries.indexOf(oldValue) + 1) % countries.length];
// Switch input value that will be posted with form
input.setAttribute('value', newValue);
// Switch graphical representation of country
img.setAttribute('src', newValue + '.png');
};
这里的例子http://jsbin.com/alasip/1/edit