nwjs/nw.js · error · TypeError

'checked' property is only available for checkbox

Error message

'checked' property is only available for checkbox

What it means

The `checked` setter throws a TypeError unless the item's type is 'checkbox'. The getter, by contrast, returns undefined for non-checkbox items. So reading is safe but writing is rejected. This matches the constructor rule that only checkbox items carry checkable state.

Source

Thrown at src/api/menuitem/menuitem.js:165

MenuItem.prototype.__defineGetter__('modifiers', function() {
  return this.handleGetter('modifiers');
});

MenuItem.prototype.__defineSetter__('modifiers', function(val) {
  this.handleSetter('modifiers', 'SetModifiers', String, val);
});

MenuItem.prototype.__defineGetter__('checked', function() {
  if (this.type != 'checkbox')
    return undefined;

  return this.handleGetter('checked');
});

MenuItem.prototype.__defineSetter__('checked', function(val) {
  if (this.type != 'checkbox')
    throw new TypeError("'checked' property is only available for checkbox");

  this.handleSetter('checked', 'SetChecked', Boolean, val);
});

MenuItem.prototype.__defineGetter__('enabled', function() {
  return this.handleGetter('enabled');
});

MenuItem.prototype.__defineSetter__('enabled', function(val) {
  this.handleSetter('enabled', 'SetEnabled', Boolean, val);
});

MenuItem.prototype.__defineGetter__('submenu', function() {
  return v8_util.getHiddenValue(this, 'submenu');
});

MenuItem.prototype.__defineSetter__('submenu', function(val) {
  if (v8_util.getConstructorName(val) != 'Menu')

View on GitHub (pinned to e15da848e9)

Solutions

Construct the item as type 'checkbox' if you need checkable state.
Guard the assignment: `if (item.type === 'checkbox') item.checked = val;`.
To convert, rebuild the item as a checkbox (type is immutable — see error 13).

Example fix

// before
var item = new nw.MenuItem({ label: 'Option' }); // type defaults to normal
item.checked = true; // throws

// after
var item = new nw.MenuItem({ type: 'checkbox', label: 'Option', checked: true });

Defensive patterns

Strategy: validation

Validate before calling

function setChecked(item, val) {
  if (item.type !== 'checkbox')
    throw new TypeError('checked only valid for checkbox items');
  item.checked = val;
}

Type guard

function isCheckboxItem(item) { return item.type === 'checkbox'; }

Try / catch

try { item.checked = val; }
catch (e) {
  if (e instanceof TypeError && /checkbox/.test(e.message)) {
    // rebuild as checkbox (type is immutable; see error 13)
    throw new Error('Item is not a checkbox; rebuild it to use checked.');
  } throw e;
}

Prevention

Only set `checked` on items built with type 'checkbox'.
Guard assignments with an item.type check.
Model toggles with checkbox items from the start.

When it happens

Trigger: Assigning `normalItem.checked = true` or `separatorItem.checked = false`. The item was created with type 'normal' (the default) and the developer tries to toggle it.

Common situations: Building toggle behavior on a normal item by mistake. Conditional code that sets `checked` without first checking the item type. Copying state between items of different types.

Related errors

AI-assisted analysis of nwjs/nw.js@e15da848e9 (2026-08-13). Data as JSON: /api/errors/6457d1c79a252de0. Report an issue: GitHub.