KeyboardEvent.getModifierState()

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

• 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

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In old implementations and outdated specifications, it returned true when a modifier which is the typical modifier key for the shortcut key is pressed.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;
  }
}

Specifications

Browser compatibility

[1]: WebKit bug #40999

See also

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