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 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.
It runs without any hooks specified
hooks.execPre('cook', null, function() {
done();
});
It runs basic serial pre hooks
pre hook functions take one parameter, a "done" function that you execute when your pre hook is finished.
var count = 0;
hooks.pre('cook', function(done) {
++count;
done();
});
hooks.execPre('cook', null, function() {
assert.equal(1, count);
done();
});
It can run multipe pre hooks
var count1 = 0;
var count2 = 0;
hooks.pre('cook', function(done) {
++count1;
done();
});
hooks.pre('cook', function(done) {
++count2;
done();
});
hooks.execPre('cook', null, function() {
assert.equal(1, count1);
assert.equal(1, count2);
done();
});
It can run fully synchronous pre hooks
If your pre hook function takes no parameters, its assumed to be fully synchronous.
var count1 = 0;
var count2 = 0;
hooks.pre('cook', function() {
++count1;
});
hooks.pre('cook', function() {
++count2;
});
hooks.execPre('cook', null, function(error) {
assert.equal(null, error);
assert.equal(1, count1);
assert.equal(1, count2);
done();
});
It properly attaches context to pre hooks
Pre save hook functions are bound to the second parameter to execPre()
hooks.pre('cook', function(done) {
this.bacon = 3;
done();
});
hooks.pre('cook', function(done) {
this.eggs = 4;
done();
});
var obj = { bacon: 0, eggs: 0 };
// In the pre hooks, `this` will refer to `obj`
hooks.execPre('cook', obj, function(error) {
assert.equal(null, error);
assert.equal(3, obj.bacon);
assert.equal(4, obj.eggs);
done();
});
It can execute parallel (async) pre hooks
Like the hooks module, you can declare "async" pre hooks - these take two
parameters, the functions next() and done(). next() passes control to
the next pre hook, but the underlying function won't be called until all
async pre hooks have called done().
hooks.pre('cook', true, function(next, done) {
this.bacon = 3;
next();
setTimeout(function() {
done();
}, 5);
});
hooks.pre('cook', true, function(next, done) {
next();
var _this = this;
setTimeout(function() {
_this.eggs = 4;
done();
}, 10);
});
hooks.pre('cook', function(next) {
this.waffles = false;
next();
});
var obj = { bacon: 0, eggs: 0 };
hooks.execPre('cook', obj, function() {
assert.equal(3, obj.bacon);
assert.equal(4, obj.eggs);
assert.equal(false, obj.waffles);
done();
});
It supports returning a promise
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.
hooks.pre('cook', function() {
return new Promise(resolve => {
setTimeout(() => {
this.bacon = 3;
resolve();
}, 100);
});
});
var obj = { bacon: 0 };
hooks.execPre('cook', obj, function() {
assert.equal(3, obj.bacon);
done();
});
post hooks
It runs without any hooks specified
hooks.execPost('cook', null, [1], function(error, eggs) {
assert.ifError(error);
assert.equal(1, eggs);
done();
});
It executes with parameters passed in
hooks.post('cook', function(eggs, bacon, callback) {
assert.equal(1, eggs);
assert.equal(2, bacon);
callback();
});
hooks.execPost('cook', null, [1, 2], function(error, eggs, bacon) {
assert.ifError(error);
assert.equal(1, eggs);
assert.equal(2, bacon);
done();
});
It can use synchronous post hooks
var execed = {};
hooks.post('cook', function(eggs, bacon) {
execed.first = true;
assert.equal(1, eggs);
assert.equal(2, bacon);
});
hooks.post('cook', function(eggs, bacon, callback) {
execed.second = true;
assert.equal(1, eggs);
assert.equal(2, bacon);
callback();
});
hooks.execPost('cook', null, [1, 2], function(error, eggs, bacon) {
assert.ifError(error);
assert.equal(2, Object.keys(execed).length);
assert.ok(execed.first);
assert.ok(execed.second);
assert.equal(1, eggs);
assert.equal(2, bacon);
done();
});
wrap()
It wraps pre and post calls into one call
hooks.pre('cook', true, function(next, done) {
this.bacon = 3;
next();
setTimeout(function() {
done();
}, 5);
});
hooks.pre('cook', true, function(next, done) {
next();
var _this = this;
setTimeout(function() {
_this.eggs = 4;
done();
}, 10);
});
hooks.pre('cook', function(next) {
this.waffles = false;
next();
});
hooks.post('cook', function(obj) {
obj.tofu = 'no';
});
var obj = { bacon: 0, eggs: 0 };
var args = [obj];
args.push(function(error, result) {
assert.ifError(error);
assert.equal(null, error);
assert.equal(3, obj.bacon);
assert.equal(4, obj.eggs);
assert.equal(false, obj.waffles);
assert.equal('no', obj.tofu);
assert.equal(obj, result);
done();
});
hooks.wrap(
'cook',
function(o, callback) {
assert.equal(3, obj.bacon);
assert.equal(4, obj.eggs);
assert.equal(false, obj.waffles);
assert.equal(undefined, obj.tofu);
callback(null, o);
},
obj,
args);
createWrapper()
It wraps wrap() into a callable function
hooks.pre('cook', true, function(next, done) {
this.bacon = 3;
next();
setTimeout(function() {
done();
}, 5);
});
hooks.pre('cook', true, function(next, done) {
next();
var _this = this;
setTimeout(function() {
_this.eggs = 4;
done();
}, 10);
});
hooks.pre('cook', function(next) {
this.waffles = false;
next();
});
hooks.post('cook', function(obj) {
obj.tofu = 'no';
});
var obj = { bacon: 0, eggs: 0 };
var cook = hooks.createWrapper(
'cook',
function(o, callback) {
assert.equal(3, obj.bacon);
assert.equal(4, obj.eggs);
assert.equal(false, obj.waffles);
assert.equal(undefined, obj.tofu);
callback(null, o);
},
obj);
cook(obj, function(error, result) {
assert.ifError(error);
assert.equal(3, obj.bacon);
assert.equal(4, obj.eggs);
assert.equal(false, obj.waffles);
assert.equal('no', obj.tofu);
assert.equal(obj, result);
done();
});
clone()
It clones a Kareem object
var k1 = new Kareem();
k1.pre('cook', function() {});
k1.post('cook', function() {});
var k2 = k1.clone();
assert.deepEqual(['cook'], Object.keys(k2._pres));
assert.deepEqual(['cook'], Object.keys(k2._posts));
merge()
It pulls hooks from another Kareem object
var k1 = new Kareem();
var test1 = function() {};
k1.pre('cook', test1);
k1.post('cook', function() {});
var k2 = new Kareem();
var test2 = function() {};
k2.pre('cook', test2);
var k3 = k2.merge(k1);
assert.equal(k3._pres['cook'].length, 2);
assert.equal(k3._pres['cook'][0].fn, test2);
assert.equal(k3._pres['cook'][1].fn, test1);
assert.equal(k3._posts['cook'].length, 1);