The HTML Label Element (<label>) represents a caption for an item in a user interface. It can be associated with a control either by placing the control element inside the <label> element, or by using the for attribute. Such a control is called the labeled control of the label element. One input can be associated with multiple labels.
The HTML select (<select>) element represents a control that presents a menu of options. The options within the menu are represented by <option> elements, which can be grouped by <optgroup> elements. Options can be pre-selected for the user.
The FormData object lets you compile a set of key/value pairs to send using XMLHttpRequest. It is primarily intended for use in sending form data, but can be used independently from forms in order to transmit keyed data. The transmitted data is in the same format that the form's submit() method would use to send the data if the form's encoding type were set to multipart/form-data.
The HTMLLabelElement.htmlFor property reflects the value of the for content property. That means that this script-accessible property is used to set and read the value of the content property for, which is the ID of the label's associated control element.
The HTMLSelectElement.autofocus property is a Boolean that reflects the autofocus HTML attribute, which indicates whether the associated <select> element will get input focus when the page loads, unless the user overrides it.
The HTML element <input> is used to create interactive controls for web-based forms in order to accept data from the user. How an <input> works varies considerably depending on the value of its type attribute.
The read-only HTMLLabelElement.control property returns a reference to the control (in the form of an object of type HTMLElement or one of its derivatives) with which the <label> element is associated, or null if the label isn't associated with a control.
The read-only HTMLLabelElement.form property returns an HTMLFormElement object which represents the form of which the label's associated control is a part, or null if there is either no associated control, or if that control isn't in a form.
The HTMLOptGroupElement interface provides special properties and methods (beyond the regular HTMLElement object interface they also have available to them by inheritance) for manipulating the layout and presentation of <optgroup> elements.
The ValidityState interface represents the validity states that an element can be in, with respect to constraint validation. Together, they help explain why an element's value fails to validate, if it's not valid.