function addHidden(theForm, key, value) {
    // Create a hidden input element, and append it to the form:
    var input = document.createElement('input');
    input.type = 'hidden';
    input.name = key; //name-as-seen-at-the-server
    input.value = value;
    theForm.appendChild(input);
}

// Form reference:
var theForm = document.forms['detParameterForm'];

// Add data:
addHidden(theForm, 'key-one', 'value');

function addHidden(theForm, key, value) {
    // Create a hidden input element, and append it to the form:
    var input = document.createElement('input');
    input.type = 'hidden';
    input.name = key; //name-as-seen-at-the-server
    input.value = value;
    theForm.appendChild(input);
}

// Form reference:
var theForm = document.forms['detParameterForm'];

// Add data:
addHidden(theForm, 'key-one', 'value');

如果你想添加更多的属性，就像这样做:

$('<input>').attr('type','hidden').attr('name','foo[]').attr('value','bar').appendTo('form');

Or

$('<input>').attr({
    type: 'hidden',
    id: 'foo',
    name: 'foo[]',
    value: 'bar'
}).appendTo('form');

和David的一样，但是没有attr()

$('<input>', {
    type: 'hidden',
    id: 'foo',
    name: 'foo',
    value: 'bar'
}).appendTo('form');

$('<input>').attr('type','hidden').appendTo('form');

回答你的第二个问题:

$('<input>').attr({
    type: 'hidden',
    id: 'foo',
    name: 'bar'
}).appendTo('form');

$('#myformelement').append('<input type="hidden" name="myfieldname" value="myvalue" />');