vm.$watch( expOrFn, callback, [options] ) Arguments: {String | Function} expOrFn {Function} callback {Object} [options]{Boolean} deep {Boolean} immediate Returns: {Function} unwatch Usage: Watch an expression or a computed function on the Vue instance for changes. The callback gets called with the new value and the old value. The expression can be a single keypath or any valid binding expressions. Note: when mutating (rather than replacing) an Object or an Array, the old value will be

Vue.delete( object, key ) Arguments: {Object} object {String} key Usage: Delete a property on an object. If the object is reactive, ensure the deletion triggers view updates. This is primarily used to get around the limitation that Vue cannot detect property deletions, but you should rarely need to use it. See also: Reactivity in Depth

vm.$root Type: Vue instance Read only Details: The root Vue instance of the current component tree. If the current instance has no parents this value will be itself.

Vue.component( id, [definition] ) Arguments: {String} id {Function | Object} [definition] Usage: Register or retrieve a global component. // register an extended constructor Vue.component('my-component', Vue.extend({ /* ... */ })) // register an options object (automatically call Vue.extend) Vue.component('my-component', { /* ... */ }) // retrieve a registered component (always return constructor) var MyComponent = Vue.component('my-component') See also: Components.

vm.$set( keypath, value ) Arguments: {String} keypath {*} value Usage: Set a data value on the Vue instance given a valid keypath. In most cases you should prefer setting properties using plain object syntax, e.g. vm.a.b = 123. This method is only needed in two scenarios: When you have a keypath string and want to dynamically set the value using that keypath. When you want to set a property that doesn’t exist. If the path doesn’t exist it will be recursively created and made reactive. If

Vue.directive( id, [definition] ) Arguments: {String} id {Function | Object} [definition] Usage: Register or retrieve a global directive. // register Vue.directive('my-directive', { bind: function () {}, update: function () {}, unbind: function () {} }) // register (simple function directive) Vue.directive('my-directive', function () { // this will be called as `update` }) // getter, return the directive definition if registered var myDirective = Vue.directive('my-directive') See

vm.$options Type: Object Read only Details: The instantiation options used for the current Vue instance. This is useful when you want to include custom properties in the options: new Vue({ customOption: 'foo', created: function () { console.log(this.$options.customOption) // -> 'foo' } })

vm.$once( event, callback ) Arguments: {String} event {Function} callback Usage: Listen for a custom event, but only once. The listener will be removed once it triggers for the first time.

vm.$parent Type: Vue instance Read only Details: The parent instance, if the current instance has one.

vm.$off( [event, callback] ) Arguments: {String} [event] {Function} [callback] Usage: Remove event listener(s). If no arguments are provided, remove all event listeners; If only the event is provided, remove all listeners for that event; If both event and callback are given, remove the listener for that specific callback only.