本段代码摘取自jquery.form.js中，由于觉得该方法的使用性非常强，同时也可独立拿出来使用。
该段代码言简意赅可以很好的作为学习参考。
复制代码 代码如下:
/**
 * clears the form data. takes the following actions on the form's input fields:
 * - input text fields will have their 'value' property set to the empty string
 * - select elements will have their 'selectedindex' property set to -1
 * - checkbox and radio inputs will have their 'checked' property set to false
 * - inputs of type submit, button, reset, and hidden will *not* be effected
 * - button elements will *not* be effected
 */
$.fn.clearform = function(includehidden) {
    return this.each(function() {
        $('input,select,textarea', this).clearfields(includehidden);   //this表示设置上下文环境，有多个表单时只作用调用的表单
    });
};$.fn.clearfields = $.fn.clearinputs = function(includehidden) {
    var re = /^(?:color|date|datetime|email|month|number|password|range|search|tel|text|time|url|week)$/i; // 'hidden' is not in this list
    return this.each(function() {
        var t = this.type, tag = this.tagname.tolowercase();
        if (re.test(t) || tag == 'textarea') {
            this.value = '';
        }
        else if (t == 'checkbox' || t == 'radio') {
            this.checked = false;
        }
        else if (tag == 'select') {
            this.selectedindex = -1;
        }
        else if (t == file) {
            if (/msie/.test(navigator.useragent)) {
                 $(this).replacewith($(this).clone(true));
            } else {
                 $(this).val('');
            }
       }
        else if (includehidden) {
            // includehidden can be the value true, or it can be a selector string
            // indicating a special test; for example:
            // $('#myform').clearform('.special:hidden')
            // the above would clean hidden inputs that have the class of 'special'
            if ( (includehidden === true && /hidden/.test(t)) ||
                 (typeof includehidden == 'string' && $(this).is(includehidden)) ) {
                this.value = '';
            }
        }
    });
};