app-history

app-history is an extension to history designed for use in progressive web apps. The API is a superset of history so you can use it as a drop-in replacement in react-router for example. TypeScript definitions are included.

Objective

The primary objective for app-history is to help developers implement back/home-buttons in progressive web apps.

When building a progressive web app you probably want to include a back-button in the user interface to support navigation in standalone mode (without browser chrome).

blah blah blah back button options

Another useful feature provided by app-history is the ability to clear the history forward stack.

blah blah blah wizard/stepper options

Installation

Using NPM and a bundler (like webpack):

npm install --save app-history

Then create an App History object in your code like this:

import { createAppHistory } from "app-history";
const history = createAppHistory();
await history.init();

Use it with react-router something like this:

import * as React from "react";
import { render } from "react-dom";
import { Router } from "react-router";
import { createAppHistory } from "app-history";

import { App } from "./App"; // Your app root component

// Create App History object (extending Browser History)
const history = createAppHistory();
await history.init();

// Create a <div> that will host the App component
const root = document.createElement("div");
document.body.appendChild(root);

// Tell React to render our app. Wrap it inside a Router component
// which is configured to use the App History object.
render(
    <Router history={history}>
        <App/>
    </Router>,
    root
);

---

Alternatively, you can load it directly from the UNPKG CDN using vanilla HTML and JavaScript:

<script src="https://unpkg.com/history/umd/history.min.js"></script>
<script src="https://unpkg.com/app-history/dist/app-history.js"></script>

Notice that you'll have to load the history UMD package too

Then create an App History object in your code like this:

const history = AppHistory.createAppHistory({ provider: History });
history.init().then(function () {
    // do stuff
});

app-history is built for ES5 but require support for Promise objects. To ensure compatibility you may want to load a Promise polyfill too.

Usage

Going back

TODO

Going home

TODO

Cutting history

TODO

A note on initialization

Blah blah. Why it's needed and Implicit if you wish

In-app navigation depth

The depth property of an app-history object lets you know how deep into the app you've gone, and thereby how far back you can go and still remain inside the current app session:

console.log("We can navigate back ", history.depth, " entry/entries and still be in this app session");

Suppressing notifications and block prompts

An history object lets you listen on location changes and conditionally block transitions, using listen and block respectively.

If you which to temporarily pause notifications and prompts you can do:

const resume = history.suppress();

// this will not notify listeners or invoke block prompt
history.pushState("foo", "bar");

// resume normal processing when you're done with the secret stuff
resume();

Or using a callback action:

history.suppressWhile(() => {
    // code in this callback won't notify listeners or invoke block prompt
});

suppressWhile returns a Promise object and will await a Promise object returned by the callback function.

You can at any time determine whether notifications and prompts are being suppressed:

console.log("Suppression is ", history.isSuppressed ? "active" : "inactive");

Async promises

app-history return promises from all methods that may trigger a location change. These promises are resolved when the new location has been applied, or rejected in case the change is blocked.

This includes the following methods from history:

• go
• goBack
• goForward
• push
• replace

And these extension methods:

• cut
• findLast
• goHome
• init
• suppressWhile
• whenIdle

You can determine whether app-history is currently processing an async operation by reading the isBusy property:

console.log("App history is ", history.isBusy ? "busy" : "idle");

Inspecting the in-app back stack

TODO

Use a custom underlying history object

createAppHistory will, by default, create a new browser history using createBrowserHistory from the history package.

You can instruct app-history to use createMemoryHistory (also from the history package) instead, which is helpful when testing your code in a non-browser environment:

const history = createAppHistory({
    mode: "memory"
});

If you want to provide another underlying history object you can do so (however, it is strongly recommended that you only access the underlying history object via the newly returned app-history extension to avoid confusion):

const history = createAppHistory({
    provider: myHistoryObjectProvider
});

The supplied provider object must declare a function named createBrowserHistory when mode is omitted or set to "browser", or a function named createMemoryHistory when mode is set to "memory".

app-history will invoke the provided function with a configuration object containing a getUserConfirmation function, no matter whether such a configuration function was passed to createAppHistory or not.

app-history is based on HTML5 History API state objects. So make sure that the underlying history object has support for that.

Specifying a custom block prompt

By default, app-history will (just like history) use window.confirm to display a prompt when navigation is blocked. You can provide a custom prompt to createAppHistory:

const history = createAppHistory({
    getUserConfirmation(message, callback) {
        callback(window.confirm(message));
    }
});

Please refer to the history package for details.

Configure the internal cache limit

app-history will internally store some meta information in HTML5 History API state objects. One piece of information is a cache of app-specific paths in the history back stack. By default, the cache is limited to 20 entries. If you want to change this you can do so:

const history = createAppHistory({
    cacheLimit: 5 // Keep at most five paths cached in my state objects
});

If you want to disable caching:

const history = createAppHistory({
    cacheLimit: 0 // No cached paths in my state objects
});

Or if you want to let the cache grow indefinately:

const history = createAppHistory({
    cacheLimit: -1 // Cache 'em all!
});

You can read the currect cache limit like this:

console.log("The app history cache limit is set to: ", history.cacheLimit);