add types definition

src/Lifecycle.d.ts

@@ -0,0 +1,67 @@
+import { PageState } from "./PageState";
+import StateChangeEvent from "./StateChangeEvent";
+
+interface StateChangeEventListener {
+  (evt: StateChangeEvent): void;
+}
+
+interface StateChangeEventListenerObject {
+  handleEvent(evt: StateChangeEvent): void;
+}
+
+declare type StateChangeEventListenerOrStateChangeEventListenerObject =
+  | StateChangeEventListener
+  | StateChangeEventListenerObject;
+
+/**
+ * Class definition for the exported, singleton lifecycle instance.
+ */
+export default class Lifecycle extends EventTarget {
+  /**
+   * Initializes state, state history, and adds event listeners to monitor
+   * state changes.
+   */
+  /**
+   * @return {string}
+   */
+  get state(): PageState;
+  /**
+   * Returns the value of document.wasDiscarded. This is arguably unnecessary
+   * but I think there's value in having the entire API in one place and
+   * consistent across browsers.
+   * @return {boolean}
+   */
+  get pageWasDiscarded(): boolean;
+
+  addEventListener(
+    type: "statechange",
+    listener: (ev: StateChangeEvent) => void,
+    options?: boolean | AddEventListenerOptions
+  ): void;
+  addEventListener(
+    type: "statechange",
+    listener: StateChangeEventListenerOrStateChangeEventListenerObject,
+    options?: boolean | AddEventListenerOptions
+  ): void;
+  removeEventListener(
+    type: "statechange",
+    listener: (ev: StateChangeEvent) => void,
+    options?: boolean | EventListenerOptions
+  ): void;
+  removeEventListener(
+    type: "statechange",
+    listener: StateChangeEventListenerOrStateChangeEventListenerObject,
+    options?: boolean | EventListenerOptions
+  ): void;
+
+  /**
+   * @param {Symbol|Object} id A unique symbol or object identifying the
+   *.    pending state. This ID is required when removing the state later.
+   */
+  addUnsavedChanges(id: Symbol | Object): void;
+  /**
+   * @param {Symbol|Object} id A unique symbol or object identifying the
+   *.    pending state. This ID is required when removing the state later.
+   */
+  removeUnsavedChanges(id: Symbol | Object): void;
+}

src/PageState.d.ts

@@ -0,0 +1,6 @@
+export declare type PageState =
+  | "active"
+  | "passive"
+  | "hidden"
+  | "frozen"
+  | "terminated";

src/StateChangeEvent.d.ts

@@ -0,0 +1,16 @@
+import { PageState } from "./PageState";
+
+/**
+ * implements {IStateChangeEvent}
+ */
+interface StateChangeEvent extends Event {
+  newState: PageState;
+  oldState: PageState;
+  originalEvent: Event;
+}
+
+declare var StateChangeEvent: {
+  prototype: StateChangeEvent;
+};
+
+export default StateChangeEvent;

src/export.d.ts

@@ -0,0 +1,3 @@
+import Lifecycle from "./Lifecycle";
+declare const _default: Lifecycle;
+export default _default;