Tapable

The tapable packages exposes many Hook classes, which can be used to create hooks for plugins.

const {
    SyncHook,
    SyncBailHook,
    SyncWaterfallHook,
    SyncLoopHook,
    AsyncParallelHook,
    AsyncParallelBailHook,
    AsyncSequencialHook,
    AsyncSequencialBailHook,
    AsyncWaterfallHook
 } = require("tapable");

Usage

All Hook constructors take one optional argument, which is a list of argument names as strings.

const hook = new SyncHook(["arg1", "arg2", "arg3"]);

The best practice is to expose all hooks of a class in a hooks property:

class Car {
    constructor() {
        this.hooks = {
            accelerate: new SyncHook(["newSpeed"]),
            break: new SyncHook(),
            calculateRoutes: new AsyncParallelHook(["source", "target", "routesList"])
        };
    }

    /* ... */
}

Other people can now use these hooks:

const myCar = new Car();

// Use the tap method to add a consument
myCar.hooks.break.tap("WarningLampPlugin", () => warningLamp.on());

It's required to pass a name to identify the plugin/reason.

You may receive arguments:

myCar.hooks.accelerate.tap("LoggerPlugin", newSpeed => console.log(`Accelerating to ${newSpeed}`));

For sync hooks tap is the only valid method to add a plugin. Async hooks also support async plugins:

myCar.hooks.calculateRoutes.tapPromise("GoogleMapsPlugin", (source, target, routesList) => {
    // return a promise
    return google.maps.findRoute(source, target).then(route => {
        routesList.add(route);
    });
});
myCar.hooks.calculateRoutes.tapAsync("BingMapsPlugin", (source, target, routesList, callback) => {
    bing.findRoute(source, target, (err, route) => {
        if(err) return callback(err);
        routesList.add(route);
        // call the callback
        callback();
    });
});

// You can still use sync plugins
myCar.hooks.calculateRoutes.tap("CachedRoutesPlugin", (source, target, routesList) => {
    const cachedRoute = cache.get(source, target);
    if(cachedRoute)
        routesList.add(cachedRoute);
})

The class declaring these hooks need to call them:

class Car {
    /* ... */

    setSpeed(newSpeed) {
        this.hooks.accelerate.call(newSpeed);
    }

    useNavigationSystemPromise(source, target) {
        const routesList = new List();
        return this.hooks.calculateRoutes.promise(source, target, routesList).then(() => {
            return routesList.getRoutes();
        });
    }

    useNavigationSystemAsync(source, target, callback) {
        const routesList = new List();
        this.hooks.calculateRoutes.callAsync(source, target, routesList, err => {
            if(err) return callback(err);
            callback(null, routesList.getRoutes());
        });
    }
}

The Hook will compile a method with the most efficient way of running your plugins. It generates code depending on:

• The number of registered plugins (none, one, many)
• The kind of registered plugins (sync, async, promise)
• The used call method (sync, async, promise)
• The number of arguments
• Whether interception is used

This ensures fastest possible execution.

Interception

All Hooks offer an additional interception API:

myCar.hooks.calculateRoutes.intercept({
    call: (source, target, routesList) => {
        console.log("Starting to calculate routes");
    },
    tap: (tapInfo) => {
        // tapInfo = { type: "promise", name: "GoogleMapsPlugin", fn: ... }
        console.log(`${tapInfo.name} is doing it's job`);
        return tapInfo; // may return a new tapInfo object
    }
})

Tapable is a class for plugin binding and applying.

Just extend it.

function MyClass() {
    Tapable.call(this);
}

MyClass.prototype = Object.create(Tapable.prototype);

MyClass.prototype.method = function() {};

Or mix it in.

function MyClass2() {
    EventEmitter.call(this);
    Tapable.call(this);
}

MyClass2.prototype = Object.create(EventEmitter.prototype);
Tapable.mixin(MyClass2.prototype);

MyClass2.prototype.method = function() {};

Public functions

apply

void apply(plugins: Plugin...)

Attaches all plugins passed as arguments to the instance, by calling apply on them.

plugin

void plugin(names: string|string[], handler: Function)

names are the names (or a single name) of the plugin interfaces the class provides.

handler is a callback function. The signature depends on the class. this is the instance of the class.

Protected functions

applyPlugins

void applyPlugins(name: string, args: any...)

Synchronously applies all registered handlers for name. The handler functions are called with all args.

applyPluginsWaterfall

any applyPluginsWaterfall(name: string, init: any, args: any...)

Synchronously applies all registered handlers for name. The handler functions are called with the return value of the previous handler and all args. For the first handler init is used and the return value of the last handler is return by applyPluginsWaterfall

applyPluginsAsync

void applyPluginsAsync(
    name: string,
    args: any...,
    callback: (err?: Error) -> void
)

Asynchronously applies all registered handlers for name. The handler functions are called with all args and a callback function with the signature (err?: Error) -> void. The handler functions are called in order of registration.

callback is called after all handlers are called.

applyPluginsBailResult

any applyPluginsBailResult(name: string, args: any...)

Synchronously applies all registered handlers for name. The handler function are called with all args. If a handler function returns something !== undefined, the value is returned and no more handlers are applied.

applyPluginsAsyncWaterfall

applyPluginsAsyncWaterfall(
    name: string,
    init: any,
    callback: (err: Error, result: any) -> void
)

Asynchronously applies all registered handlers for name. The handler functions are called with the current value and a callback function with the signature (err: Error, nextValue: any) -> void. When called, nextValue is the current value for the next handler. The current value for the first handler is init. After all handlers are applied, callback is called with the last value. If any handler passes a value for err, the callback is called with this error and no more handlers are called.

applyPluginsAsyncSeries

applyPluginsAsyncSeries(
    name: string,
    args: any...,
    callback: (err: Error, result: any) -> void
)

Asynchronously applies all registered handlers for name. The handler functions are called with all args and a callback function with the signature (err: Error) -> void. The handlers are called in series, one at a time. After all handlers are applied, callback is called. If any handler passes a value for err, the callback is called with this error and no more handlers are called.

applyPluginsParallel

applyPluginsParallel(
    name: string,
    args: any...,
    callback: (err?: Error) -> void
)

Applies all registered handlers for name in parallel. The handler functions are called with all args and a callback function with the signature (err?: Error) -> void. The callback function is called when all handlers have called the callback without err. If any handler calls the callback with err, callback is invoked with this error and the other handlers are ignored.

applyPluginsParallelBailResult

applyPluginsParallelBailResult(
    name: string,
    args: any...,
    callback: (err: Error, result: any) -> void
)

Applies all registered handlers for name in parallel. The handler functions are called with all args and a callback function with the signature (err?: Error) -> void. Handler functions must call the callback. They can either pass an error, pass undefined, or pass a value. The first result (either error or value) which is not undefined is passed to the callback. The order is defined by registration, not by the speed of the handler function.

hasPlugins

hasPlugins(
    name: string
)

Returns true, if plugins are registered for this name.