kareem


Re-imagined take on the hooks module, meant to offer additional flexibility in allowing you to execute hooks whenever necessary, as opposed to simply wrapping a single function.

Named for the NBA's 2nd all-time leading scorer Kareem Abdul-Jabbar, known for his mastery of the hook shot

API

pre hooks

Much like hooks, kareem lets you define
pre and post hooks: pre hooks are called before a given function executes.
Unlike hooks, kareem stores hooks and other internal state in a separate
object, rather than relying on inheritance. Furthermore, kareem exposes
an execPre() function that allows you to execute your pre hooks when
appropriate, giving you more fine-grained control over your function hooks.

$3

``javascript
await hooks.execPre('cook', null);
`

$3

pre hook functions can return a promise that resolves when finished.

`javascript
let count = 0;

hooks.pre('cook', function() {
++count;
return Promise.resolve();
});

await hooks.execPre('cook', null);
assert.equal(1, count);
`

$3

`javascript
let count1 = 0;
let count2 = 0;

hooks.pre('cook', function() {
++count1;
return Promise.resolve();
});

hooks.pre('cook', function() {
++count2;
return Promise.resolve();
});

await hooks.execPre('cook', null);
assert.equal(1, count1);
assert.equal(1, count2);
`

$3

If your pre hook function takes no parameters, its assumed to be
fully synchronous.

`javascript
let count1 = 0;
let count2 = 0;

hooks.pre('cook', function() {
++count1;
});

hooks.pre('cook', function() {
++count2;
});

await hooks.execPre('cook', null);
assert.equal(1, count1);
assert.equal(1, count2);
`

$3

Pre save hook functions are bound to the second parameter to execPre()

`javascript
hooks.pre('cook', function() {
this.bacon = 3;
});

hooks.pre('cook', function() {
this.eggs = 4;
});

const obj = { bacon: 0, eggs: 0 };

// In the pre hooks, this will refer to obj
await hooks.execPre('cook', obj);
assert.equal(3, obj.bacon);
assert.equal(4, obj.eggs);
`

$3

You can also return a promise from your pre hooks instead of calling
next(). When the returned promise resolves, kareem will kick off the
next middleware.

`javascript
hooks.pre('cook', function() {
return new Promise(resolve => {
setTimeout(() => {
this.bacon = 3;
resolve();
}, 100);
});
});

const obj = { bacon: 0 };

await hooks.execPre('cook', obj);
assert.equal(3, obj.bacon);
`

$3

You can pass a filter option to execPre() to select which hooks
to run. The filter function receives each hook object and should return
true to run the hook or false to skip it.

`javascript
const execed = [];

const fn1 = function() { execed.push('first'); };
fn1.skipMe = true;
hooks.pre('cook', fn1);

const fn2 = function() { execed.push('second'); };
hooks.pre('cook', fn2);

// Only runs fn2, skips fn1 because fn1.skipMe is true
await hooks.execPre('cook', null, [], {
filter: hook => !hook.fn.skipMe
});

assert.deepStrictEqual(execed, ['second']);
`

post hooks

$3

`javascript
const [eggs] = await hooks.execPost('cook', null, [1]);
assert.equal(eggs, 1);
`

$3

`javascript
hooks.post('cook', function(eggs, bacon, callback) {
assert.equal(eggs, 1);
assert.equal(bacon, 2);
callback();
});

const [eggs, bacon] = await hooks.execPost('cook', null, [1, 2]);
assert.equal(eggs, 1);
assert.equal(bacon, 2);
`

$3

`javascript
const execed = {};

hooks.post('cook', function(eggs, bacon) {
execed.first = true;
assert.equal(eggs, 1);
assert.equal(bacon, 2);
});

hooks.post('cook', function(eggs, bacon, callback) {
execed.second = true;
assert.equal(eggs, 1);
assert.equal(bacon, 2);
callback();
});

const [eggs, bacon] = await hooks.execPost('cook', null, [1, 2]);
assert.equal(Object.keys(execed).length, 2);
assert.ok(execed.first);
assert.ok(execed.second);
assert.equal(eggs, 1);
assert.equal(bacon, 2);
`

$3

You can also return a promise from your post hooks instead of calling
next(). When the returned promise resolves, kareem will kick off the
next middleware.

`javascript
hooks.post('cook', function() {
return new Promise(resolve => {
setTimeout(() => {
this.bacon = 3;
resolve();
}, 100);
});
});

const obj = { bacon: 0 };

await hooks.execPost('cook', obj, [obj]);
assert.equal(obj.bacon, 3);
`

$3

You can pass a filter option to execPost() to select which hooks
to run. The filter function receives each hook object and should return
true to run the hook or false to skip it.

`javascript
const execed = [];

const fn1 = function() { execed.push('first'); };
fn1.skipMe = true;
hooks.post('cook', fn1);

const fn2 = function() { execed.push('second'); };
hooks.post('cook', fn2);

// Only runs fn2, skips fn1 because fn1.skipMe is true
await hooks.execPost('cook', null, [], {
filter: hook => !hook.fn.skipMe
});

assert.deepStrictEqual(execed, ['second']);
`

wrap()

$3

`javascript
hooks.pre('cook', function() {
return new Promise(resolve => {
this.bacon = 3;
setTimeout(() => {
resolve();
}, 5);
});
});

hooks.pre('cook', function() {
this.eggs = 4;
return Promise.resolve();
});

hooks.pre('cook', function() {
this.waffles = false;
return Promise.resolve();
});

hooks.post('cook', function(obj) {
obj.tofu = 'no';
});

const obj = { bacon: 0, eggs: 0 };

const args = [obj];

const result = await hooks.wrap(
'cook',
function(o) {
assert.equal(obj.bacon, 3);
assert.equal(obj.eggs, 4);
assert.equal(obj.waffles, false);
assert.equal(obj.tofu, undefined);
return o;
},
obj,
args);

assert.equal(obj.bacon, 3);
assert.equal(obj.eggs, 4);
assert.equal(obj.waffles, false);
assert.equal(obj.tofu, 'no');
assert.equal(result, obj);
`

createWrapper()

$3

`javascript
hooks.pre('cook', function() {
this.bacon = 3;
return Promise.resolve();
});

hooks.pre('cook', function() {
return new Promise(resolve => {
this.eggs = 4;
setTimeout(function() {
resolve();
}, 10);
});
});

hooks.pre('cook', function() {
this.waffles = false;
return Promise.resolve();
});

hooks.post('cook', function(obj) {
obj.tofu = 'no';
});

const obj = { bacon: 0, eggs: 0 };

const cook = hooks.createWrapper(
'cook',
function(o) {
assert.equal(3, obj.bacon);
assert.equal(4, obj.eggs);
assert.equal(false, obj.waffles);
assert.equal(undefined, obj.tofu);
return o;
},
obj);

const result = await cook(obj);
assert.equal(obj.bacon, 3);
assert.equal(obj.eggs, 4);
assert.equal(obj.waffles, false);
assert.equal(obj.tofu, 'no');

assert.equal(result, obj);
`

clone()

$3

`javascript
const k1 = new Kareem();
k1.pre('cook', function() {});
k1.post('cook', function() {});

const k2 = k1.clone();
assert.deepEqual(Array.from(k2._pres.keys()), ['cook']);
assert.deepEqual(Array.from(k2._posts.keys()), ['cook']);
`

merge()

$3

`javascript
const k1 = new Kareem();
const test1 = function() {};
k1.pre('cook', test1);
k1.post('cook', function() {});

const k2 = new Kareem();
const test2 = function() {};
k2.pre('cook', test2);
const k3 = k2.merge(k1);
assert.equal(k3._pres.get('cook').length, 2);
assert.equal(k3._pres.get('cook')[0].fn, test2);
assert.equal(k3._pres.get('cook')[1].fn, test1);
assert.equal(k3._posts.get('cook').length, 1);
``