ValidityState object: Returns the validity state that this element is in.
string:Returns a localized message that describes the validation constraints that the control does not satisfy (if any). This is the empty string if the control is not a candidate for constraint validation (willvalidate is false), or it satisfies its constraints.
Boolean:Indicates whether the element is a candidate for constraint validation. It is false if any conditions bar it from constraint validation.
boolean:返回/ 设置 当前选中状态，当控件type 是 checkbox 或 radio 时。
boolean:返回/ 设置 the default state of a radio button or checkbox as originally specified in HTML that created this object.
boolean:indicates that the checkbox is neither on nor off. Changes the appearance to resemble a third state. Does not affect the value of the checked 属性，and clicking the checkbox will set the value to false.
string:返回/ 设置 元素的 alt 属性，包含 alternative text to use when type is image.
string:返回/ 设置 元素的 height 属性，which defines the height of the image displayed for the button, if the value of type is image.
string:返回/ 设置 元素的 src 属性，which specifies a URI for the location of an image to display on the graphical submit button, if the value of type is image; otherwise it is ignored.
string:返回/ 设置 the document's width 属性，which defines the width of the image displayed for the button, if the value of type is image.
string:Returns / Sets 元素的 accept 属性，包含 comma-separated list of file types accepted by the server when type is file.
boolean: Part of the non-standard Directory Upload API; indicates whether or not to allow directories and files both to be selected in the file list. Implemented only in Firefox and is hidden behind a preference.
Returns/accepts a FileList object, which contains a list of File objects representing the files selected for upload.
Array of FileSystemEntry objects describing the currently-selected files or directories.
string:返回/ 设置 元素的 autocomplete 属性，indicating whether the value of the control can be automatically completed by the browser. Ignored if the value of the type 属性 is hidden, checkbox, radio, file, or a button type (button, submit, reset, image). Possible values are: "on": the browser can autocomplete the value using previously stored value "off": the user must explicity enter a value
long:返回/ 设置 元素的 maxlength 属性，包含 the maximum length of characters (in Unicode code points) that the value can have. (If you set this to a negative number, an exception will be thrown.)
unsigned long:返回/ 设置 元素的 size 属性，包含 size of the control. This value is in pixels unless the value of type is text or password, in which case, it is an integer number of characters. Applies only when type is set to text, search, tel, url, email, or password; otherwise it is ignored.
string:返回/ 设置 元素的 pattern 属性，包含 a regular expression that the control's value is checked against. Use the title 属性 to describe the pattern to help the user. This 属性 applies when the value of the type 属性 is text, search, tel, url or email; otherwise it is ignored.
string:返回/ 设置 元素的 placeholder 属性，包含 a hint to the user of what can be entered in the control. The placeholder text must not contain carriage returns or line-feeds. This 属性 applies when the value of the type 属性 is text, search, tel, url or email; otherwise it is ignored.
boolean:返回/ 设置 元素的 readonly 属性，indicating that the user cannot modify the value of the control. This is ignored if the value of the type 属性 is hidden, range, color, checkbox, radio, file, or a button type.
string:返回/ 设置 元素的 min 属性，包含 the minimum (numeric or date-time) value for this item, which must not be greater than its maximum (max 属性) value.
string:返回/ 设置 元素的 max 属性，包含 the maximum (numeric or date-time) value for this item, which must not be less than its minimum (min 属性) value.
unsigned long:返回/ 设置 the beginning index of the selected text. When nothing is selected, this returns the position of the text input cursor (caret) inside of the <input> element.
unsigned long:返回/ 设置 the end index of the selected text. When there's no selection, this returns the offset of the character immediately following the current text input cursor position.
string:返回/ 设置 the direction in which selection occurred. Possible values are: "forward" if selection was performed in the start-to-end direction of the current locale, "backward" for the opposite direction, "none" if the direction is unknown."
string:返回/ 设置 the default
value as originally specified in the HTML that created this object.
string:返回/ 设置 the
directionality of the element.
string: 返回 a string 包含 a
single character that switches input focus to the control when pressed.
HTMLElement object:返回 the element pointed by the
list 属性。The property may
be null if no HTML element found in the same tree.
boolean:返回/ 设置 元素的
whether more than one value is possible (e.g., multiple files).
NodeList array:返回a list of <label>
elements that are labels for this element.
string:返回/ 设置 元素的
step 属性，which works
max to limit the increments at
which a numeric or date-time value can be set. It can be the string
any or a positive floating point number. If this is not set
to any, the control accepts only values at multiples of the
step value greater than the minimum.
Date object: Returns / Sets
the value of the element, interpreted as a date, or null if
conversion is not possible.
double: 返回the value of the element,
interpreted as one of the following, in order:
a time value
NaN if conversion is impossible
string:定义 the capitalization
behavior for user input. Valid values are none,
off, characters, words, or
Selects a range of text in the element (but does not focus it). The
optional selectionDirection parameter may be "forward" or "backward" to
establish the direction in which selection was set, or "none" if the
direction is unknown or not relevant. The default is "none". Specifying
a selectionDirection parameter sets the value of the selectionDirection
Replaces a range of text with the new text. If the
start and end arguments are not provided, the
range is assumed to be the selection.The final argument determines how
the selection should be set after the text has been replaced. The
possible values are:
Selects the newly inserted text.
Moves the selection to just before the inserted text.
Moves the selection to just after the selected text.
Attempts to preserve the selection. This is the default.
Sets a custom validity message for the element. If this message is not
the empty string, then the element is suffering from a custom validity
error, and does not validate.
Returns a Boolean that is false if the
element is a candidate for constraint validation, and it does not
satisfy its constraints. In this case, it also fires an
[`invalid`](/zh-CN/docs/Web/API/HTMLInputElement/invalid_event) event at the element. It returns
true if the element is not a candidate for constraint
validation, or if it satisfies its constraints.
Sets the files selected on the input to the given array of File objects. This is an alternative to mozSetFileNameArray() which can be used in frame scripts: a chrome script can open files as File objects and send them via message manager.