asynchronous hooks for internal functionality
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Load before-after-hook directly from cdn.skypack.dev
<script type="module">
import Hook from "https://cdn.skypack.dev/before-after-hook";
</script> |
|---|---|
| Node |
Install with import Hook from "before-after-hook"; |
// instantiate singular hook API
const hook = new Hook.Singular();
// Create a hook
async function getData(options) {
try {
const result = await hook(fetchFromDatabase, options);
return handleData(result);
} catch (error) {
return handleGetError(error);
}
}
// register before/error/after hooks.
// The methods can be async or return a promise
hook.before(beforeHook);
hook.error(errorHook);
hook.after(afterHook);
getData({ id: 123 });// instantiate hook collection API
const hookCollection = new Hook.Collection();
// Create a hook
async function getData(options) {
try {
const result = await hookCollection("get", fetchFromDatabase, options);
return handleData(result);
} catch (error) {
return handleGetError(error);
}
}
// register before/error/after hooks.
// The methods can be async or return a promise
hookCollection.before("get", beforeHook);
hookCollection.error("get", errorHook);
hookCollection.after("get", afterHook);
getData({ id: 123 });There's no fundamental difference between the Hook.Singular and Hook.Collection hooks except for the fact that a hook from a collection requires you to pass along the name. Therefore the following explanation applies to both code snippets as described above.
The methods are executed in the following order
beforeHookfetchFromDatabaseafterHookhandleData
beforeHook can mutate options before it’s passed to fetchFromDatabase.
If an error is thrown in beforeHook or fetchFromDatabase then errorHook is
called next.
If afterHook throws an error then handleGetError is called instead
of handleData.
If errorHook throws an error then handleGetError is called next, otherwise
afterHook and handleData.
You can also use hook.wrap to achieve the same thing as shown above (collection example):
hookCollection.wrap("get", async (getData, options) => {
await beforeHook(options);
try {
const result = getData(options);
} catch (error) {
await errorHook(error, options);
}
await afterHook(result, options);
});- Singular constructor
- hook.api
- hook()
- hook.before()
- hook.error()
- hook.after()
- hook.wrap()
- hook.remove()
The Hook.Singular constructor has no options and returns a hook instance with the
methods below:
const hook = new Hook.Singular();Using the singular hook is recommended for TypeScript
The singular hook is a reference to a single hook. This means that there's no need to pass along any identifier (such as a name as can be seen in the Hook.Collection API).
The API of a singular hook is exactly the same as a collection hook and we therefore suggest you read the Hook.Collection API and leave out any use of the name argument. Just skip it like described in this example:
const hook = new Hook.Singular();
// good
hook.before(beforeHook);
hook.after(afterHook);
hook(fetchFromDatabase, options);
// bad
hook.before("get", beforeHook);
hook.after("get", afterHook);
hook("get", fetchFromDatabase, options);- Collection constructor
- hookCollection.api
- hookCollection()
- hookCollection.before()
- hookCollection.error()
- hookCollection.after()
- hookCollection.wrap()
- hookCollection.remove()
The Hook.Collection constructor has no options and returns a hookCollection instance with the
methods below
const hookCollection = new Hook.Collection();Use the api property to return the public API:
- hookCollection.before()
- hookCollection.after()
- hookCollection.error()
- hookCollection.wrap()
- hookCollection.remove()
That way you don’t need to expose the hookCollection() method to consumers of your library
Invoke before and after hooks. Returns a promise.
hookCollection(nameOrNames, method /*, options */);| Argument | Type | Description | Required |
|---|---|---|---|
name |
String or Array of Strings | Hook name, for example 'save'. Or an array of names, see example below. |
Yes |
method |
Function | Callback to be executed after all before hooks finished execution successfully. options is passed as first argument |
Yes |
options |
Object | Will be passed to all before hooks as reference, so they can mutate it | No, defaults to empty object ({}) |
Resolves with whatever method returns or resolves with.
Rejects with error that is thrown or rejected with by
- Any of the before hooks, whichever rejects / throws first
method- Any of the after hooks, whichever rejects / throws first
Simple Example
hookCollection(
"save",
(record) => {
return store.save(record);
},
record
);
// shorter: hookCollection('save', store.save, record)
hookCollection.before("save", function addTimestamps(record) {
const now = new Date().toISOString();
if (record.createdAt) {
record.updatedAt = now;
} else {
record.createdAt = now;
}
});Example defining multiple hooks at once.
hookCollection(
["add", "save"],
(record) => {
return store.save(record);
},
record
);
hookCollection.before("add", function addTimestamps(record) {
if (!record.type) {
throw new Error("type property is required");
}
});
hookCollection.before("save", function addTimestamps(record) {
if (!record.type) {
throw new Error("type property is required");
}
});Defining multiple hooks is helpful if you have similar methods for which you want to define separate hooks, but also an additional hook that gets called for all at once. The example above is equal to this:
hookCollection(
"add",
(record) => {
return hookCollection(
"save",
(record) => {
return store.save(record);
},
record
);
},
record
);Add before hook for given name.
hookCollection.before(name, method);| Argument | Type | Description | Required |
|---|---|---|---|
name |
String | Hook name, for example 'save' |
Yes |
method |
Function |
Executed before the wrapped method. Called with the hook’s
options argument. Before hooks can mutate the passed options
before they are passed to the wrapped method.
|
Yes |
Example
hookCollection.before("save", function validate(record) {
if (!record.name) {
throw new Error("name property is required");
}
});Add error hook for given name.
hookCollection.error(name, method);| Argument | Type | Description | Required |
|---|---|---|---|
name |
String | Hook name, for example 'save' |
Yes |
method |
Function |
Executed when an error occurred in either the wrapped method or a
before hook. Called with the thrown error
and the hook’s options argument. The first method
which does not throw an error will set the result that the after hook
methods will receive.
|
Yes |
Example
hookCollection.error("save", (error, options) => {
if (error.ignore) return;
throw error;
});Add after hook for given name.
hookCollection.after(name, method);| Argument | Type | Description | Required |
|---|---|---|---|
name |
String | Hook name, for example 'save' |
Yes |
method |
Function |
Executed after wrapped method. Called with what the wrapped method
resolves with the hook’s options argument.
|
Yes |
Example
hookCollection.after("save", (result, options) => {
if (result.updatedAt) {
app.emit("update", result);
} else {
app.emit("create", result);
}
});Add wrap hook for given name.
hookCollection.wrap(name, method);| Argument | Type | Description | Required |
|---|---|---|---|
name |
String | Hook name, for example 'save' |
Yes |
method |
Function | Receives both the wrapped method and the passed options as arguments so it can add logic before and after the wrapped method, it can handle errors and even replace the wrapped method altogether | Yes |
Example
hookCollection.wrap("save", async (saveInDatabase, options) => {
if (!record.name) {
throw new Error("name property is required");
}
try {
const result = await saveInDatabase(options);
if (result.updatedAt) {
app.emit("update", result);
} else {
app.emit("create", result);
}
return result;
} catch (error) {
if (error.ignore) return;
throw error;
}
});See also: Test mock example
Removes hook for given name.
hookCollection.remove(name, hookMethod);| Argument | Type | Description | Required |
|---|---|---|---|
name |
String | Hook name, for example 'save' |
Yes |
beforeHookMethod |
Function |
Same function that was previously passed to hookCollection.before(), hookCollection.error(), hookCollection.after() or hookCollection.wrap()
|
Yes |
Example
hookCollection.remove("save", validateRecord);This library contains type definitions for TypeScript.
import Hook from "before-after-hook";
type TOptions = { foo: string }; // type for options
type TResult = { bar: number }; // type for result
type TError = Error; // type for error
const hook = new Hook.Singular<TOptions, TResult, TError>();
hook.before((options) => {
// `options.foo` has `string` type
// not allowed
options.foo = 42;
// allowed
options.foo = "Forty-Two";
});
const hookedMethod = hook(
(options) => {
// `options.foo` has `string` type
// not allowed, because it does not satisfy the `R` type
return { foo: 42 };
// allowed
return { bar: 42 };
},
{ foo: "Forty-Two" }
);You can choose not to pass the types for options, result or error. So, these are completely valid:
const hook = new Hook.Singular<O, R>();
const hook = new Hook.Singular<O>();
const hook = new Hook.Singular();In these cases, the omitted types will implicitly be any.
Collection also has strict type support. You can use it like this:
import { Hook } from "before-after-hook";
type HooksType = {
add: {
Options: { type: string };
Result: { id: number };
Error: Error;
};
save: {
Options: { type: string };
Result: { id: number };
};
read: {
Options: { id: number; foo: number };
};
destroy: {
Options: { id: number; foo: string };
};
};
const hooks = new Hook.Collection<HooksType>();
hooks.before("destroy", (options) => {
// `options.id` has `number` type
});
hooks.error("add", (err, options) => {
// `options.type` has `string` type
// `err` is `instanceof Error`
});
hooks.error("save", (err, options) => {
// `options.type` has `string` type
// `err` has type `any`
});
hooks.after("save", (result, options) => {
// `options.type` has `string` type
// `result.id` has `number` type
});You can choose not to pass the types altogether. In that case, everything will implicitly be any:
const hook = new Hook.Collection();Alternative imports:
import { Singular, Collection } from "before-after-hook";
const hook = new Singular();
const hooks = new Collection();Since version 1.4 the Hook constructor has been deprecated in favor of returning Hook.Singular in an upcoming breaking release.
Version 1.4 is still 100% backwards-compatible, but if you want to continue using hook collections, we recommend using the Hook.Collection constructor instead before the next release.
For even more details, check out the PR.
If before-after-hook is not for you, have a look at one of these alternatives: