KeyboardEvent.getModifierState() - Web APIs 编辑

The KeyboardEvent.getModifierState() method returns the current state of the specified modifier key: true if the modifier is active (that is the modifier key is pressed or locked), otherwise, false.

Syntax

var active = event.getModifierState(keyArg);

Returns 

A Boolean

Parameters

keyArg

A modifier key value. The value must be one of the KeyboardEvent.key values which represent modifier keys, or the string "Accel" . This is case-sensitive.

Modifier keys on Internet Explorer

IE9 uses "Scroll" for "ScrollLock" and "Win" for "OS".

Modifier keys on Gecko

When getModifierState() returns true on Gecko?

	Windows	Linux (GTK)	Mac	Android 2.3	Android 3.0 or latter
"Alt"	Either Alt key or AltGr key pressed	Alt key pressed	⌥ Option key pressed	Alt key or option key pressed
"AltGraph"	Both Alt and Ctrl keys are pressed, or AltGr key is pressed	Level 3 Shift key (or Level 5 Shift key ) pressed	⌥ Option key pressed	Not supported
"CapsLock"	During LED for ⇪ Caps Lock turned on			Not supported	While CapsLock is locked
"Control"	Either Ctrl key or AltGr key pressed	Ctrl key pressed	control key pressed	menu key pressed.	Ctrl key, control key or menu key pressed.
"Fn"	Not supported				Function key is pressed, but we're not sure what key makes the modifier state active. Fn key on Mac keyboard doesn't cause this active.
"FnLock"	Not supported
"Hyper"	Not supported
"Meta"	Not supported	Meta key pressed	⌘ Command key pressed	Not supported	⊞ Windows Logo key or command key pressed
"NumLock"	During LED for Num Lock turned on		A key on numpad pressed	Not supported	While NumLock is locked
"OS"	⊞ Windows Logo key pressed	Super key or Hyper key pressed (typically, mapped to ⊞ Windows Logo key)	Not supported
"ScrollLock"	During LED for Scroll Lock turned on	During LED for Scroll Lock turned on, but typically this isn't supported by platform	Not supported		While ScrollLock is locked
"Shift"	⇧ Shift key pressed
"Super"	Not supported
"Symbol"	Not supported
"SymbolLock"	Not supported

• On the other platforms, "Alt", "Control" and "Shift" may be supported.
• All modifiers (except "FnLock", "Hyper", "Super" and "Symbol" which are defined after Gecko implements this) are always supported for untrusted events on Gecko. This doesn't depend on the platform.

"Accel" virtual modifier

Note: The "Accel" virtual modifier has been effectively deprecated in current drafts of the DOM3 Events specification.

getModifierState() also accepts a deprecated virtual modifier named "Accel". event.getModifierState("Accel") returns true when at least one of KeyboardEvent.ctrlKey or KeyboardEvent.metaKey is true.

In old implementations and outdated specifications, it returned true when a modifier which is the typical modifier key for the shortcut key is pressed. For example, on Windows, pressing Ctrl key may make it return true. However, on Mac, pressing ⌘ Command key may make it return true. Note that which modifier key makes it return true depends on platforms, browsers, and user settings. For example, Firefox users can customize this with a pref, "ui.key.accelKey".

Example

// Ignore if following modifier is active.
if (event.getModifierState("Fn") ||
    event.getModifierState("Hyper") ||
    event.getModifierState("OS") ||
    event.getModifierState("Super") ||
    event.getModifierState("Win") /* hack for IE */) {
  return;
}

// Also ignore if two or more modifiers except Shift are active.
if (event.getModifierState("Control") +
    event.getModifierState("Alt") +
    event.getModifierState("Meta") > 1) {
  return;
}

// Handle shortcut key with standard modifier
if (event.getModifierState("Accel")) {
  switch (event.key.toLowerCase()) {
    case "c":
      if (event.getModifierState("Shift")) {
        // Handle Accel + Shift + C
        event.preventDefault(); // consume the key event
      }
      break;
    case "k":
      if (!event.getModifierState("Shift")) {
        // Handle Accel + K
        event.preventDefault(); // consume the key event
      }
      break;
  }
  return;
}

// Do somethig different for arrow keys if ScrollLock is locked.
if ((event.getModifierState("ScrollLock") ||
       event.getModifierState("Scroll") /* hack for IE */) &&
    !event.getModifierState("Control") &&
    !event.getModifierState("Alt") &&
    !event.getModifierState("Meta")) {
  switch (event.key) {
    case "ArrowDown":
    case "Down": // hack for IE and old Gecko
      event.preventDefault(); // consume the key event
      break;
    case "ArrowLeft":
    case "Left": // hack for IE and old Gecko
      // Do something different if ScrollLock is locked.
      event.preventDefault(); // consume the key event
      break;
    case "ArrowRight":
    case "Right": // hack for IE and old Gecko
      // Do something different if ScrollLock is locked.
      event.preventDefault(); // consume the key event
      break;
    case "ArrowUp":
    case "Up": // hack for IE and old Gecko
      // Do something different if ScrollLock is locked.
      event.preventDefault(); // consume the key event
      break;
  }
}

Although this example uses .getModifierState() with "Alt", "Control", "Meta" and "Shift", using event.altKey, event.ctrlKey, event.metaKey and event.shiftKey may be more preferable.

Specifications

Specification	Status	Comment
Document Object Model (DOM) Level 3 Events Specification The definition of 'getModifierState()' in that specification.	Obsolete	Initial definition (Modifier Keys spec)

Browser compatibility

BCD tables only load in the browser

See also

• The KeyboardEvent this method belongs to.
• MouseEvent.getModifierState