KeyboardEvent: getModifierState() method

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

getModifierState(key)

Parameters

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

Return value

A boolean.

Modifier keys on Firefox

When getModifierState() returns true on Firefox?

	Windows	Linux (GTK)	Mac	Android 2.3	Android 3.0 or later
`"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	❌ 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	❌ Not supported	❌ Not supported	❌ 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	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported
`"Hyper"`	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported
`"Meta"`	`⊞ Windows Logo` key pressed (from Firefox 118)	`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 (before Firefox 118)	`Super` key or `Hyper` key pressed (typically, mapped to `⊞ Windows Logo` key)	❌ Not supported	❌ Not supported	❌ 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	❌ Not supported	While `ScrollLock` is locked
`"Shift"`	`⇧ Shift` key pressed
`"Super"`	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported
`"Symbol"`	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported
`"SymbolLock"`	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	❌ 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 Firefox implements this) are always supported for untrusted events on Firefox. 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".

Examples

function handleKeyboardEvent(event) {
  // 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 something 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 Firefox
        event.preventDefault(); // consume the key event
        break;
      case "ArrowLeft":
      case "Left": // hack for IE and old Firefox
        // Do something different if ScrollLock is locked.
        event.preventDefault(); // consume the key event
        break;
      case "ArrowRight":
      case "Right": // hack for IE and old Firefox
        // Do something different if ScrollLock is locked.
        event.preventDefault(); // consume the key event
        break;
      case "ArrowUp":
      case "Up": // hack for IE and old Firefox
        // Do something different if ScrollLock is locked.
        event.preventDefault(); // consume the key event
        break;
    }
  }
}

Note: 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
UI Events # dom-keyboardevent-getmodifierstate

Browser compatibility

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