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421 lines
8.4 KiB
421 lines
8.4 KiB
# kareem
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[](https://travis-ci.org/vkarpov15/kareem)
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[](https://coveralls.io/r/vkarpov15/kareem)
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Re-imagined take on the [hooks](http://npmjs.org/package/hooks) module, meant to offer additional flexibility in allowing you to execute hooks whenever necessary, as opposed to simply wrapping a single function.
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Named for the NBA's all-time leading scorer Kareem Abdul-Jabbar, known for his mastery of the [hook shot](http://en.wikipedia.org/wiki/Kareem_Abdul-Jabbar#Skyhook)
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<img src="http://upload.wikimedia.org/wikipedia/commons/0/00/Kareem-Abdul-Jabbar_Lipofsky.jpg" width="220">
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# API
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## pre hooks
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Much like [hooks](https://npmjs.org/package/hooks), kareem lets you define
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pre and post hooks: pre hooks are called before a given function executes.
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Unlike hooks, kareem stores hooks and other internal state in a separate
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object, rather than relying on inheritance. Furthermore, kareem exposes
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an `execPre()` function that allows you to execute your pre hooks when
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appropriate, giving you more fine-grained control over your function hooks.
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#### It runs without any hooks specified
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```javascript
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hooks.execPre('cook', null, function() {
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// ...
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});
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```
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#### It runs basic serial pre hooks
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pre hook functions take one parameter, a "done" function that you execute
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when your pre hook is finished.
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```javascript
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var count = 0;
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hooks.pre('cook', function(done) {
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++count;
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done();
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});
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hooks.execPre('cook', null, function() {
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assert.equal(1, count);
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});
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```
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#### It can run multipe pre hooks
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```javascript
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var count1 = 0;
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var count2 = 0;
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hooks.pre('cook', function(done) {
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++count1;
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done();
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});
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hooks.pre('cook', function(done) {
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++count2;
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done();
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});
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hooks.execPre('cook', null, function() {
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assert.equal(1, count1);
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assert.equal(1, count2);
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});
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```
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#### It can run fully synchronous pre hooks
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If your pre hook function takes no parameters, its assumed to be
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fully synchronous.
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```javascript
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var count1 = 0;
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var count2 = 0;
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hooks.pre('cook', function() {
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++count1;
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});
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hooks.pre('cook', function() {
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++count2;
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});
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hooks.execPre('cook', null, function(error) {
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assert.equal(null, error);
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assert.equal(1, count1);
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assert.equal(1, count2);
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});
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```
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#### It properly attaches context to pre hooks
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Pre save hook functions are bound to the second parameter to `execPre()`
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```javascript
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hooks.pre('cook', function(done) {
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this.bacon = 3;
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done();
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});
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hooks.pre('cook', function(done) {
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this.eggs = 4;
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done();
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});
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var obj = { bacon: 0, eggs: 0 };
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// In the pre hooks, `this` will refer to `obj`
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hooks.execPre('cook', obj, function(error) {
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assert.equal(null, error);
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assert.equal(3, obj.bacon);
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assert.equal(4, obj.eggs);
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});
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```
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#### It can execute parallel (async) pre hooks
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Like the hooks module, you can declare "async" pre hooks - these take two
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parameters, the functions `next()` and `done()`. `next()` passes control to
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the next pre hook, but the underlying function won't be called until all
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async pre hooks have called `done()`.
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```javascript
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hooks.pre('cook', true, function(next, done) {
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this.bacon = 3;
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next();
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setTimeout(function() {
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done();
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}, 5);
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});
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hooks.pre('cook', true, function(next, done) {
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next();
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var _this = this;
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setTimeout(function() {
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_this.eggs = 4;
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done();
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}, 10);
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});
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hooks.pre('cook', function(next) {
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this.waffles = false;
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next();
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});
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var obj = { bacon: 0, eggs: 0 };
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hooks.execPre('cook', obj, function() {
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assert.equal(3, obj.bacon);
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assert.equal(4, obj.eggs);
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assert.equal(false, obj.waffles);
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});
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```
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#### It supports returning a promise
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You can also return a promise from your pre hooks instead of calling
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`next()`. When the returned promise resolves, kareem will kick off the
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next middleware.
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```javascript
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hooks.pre('cook', function() {
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return new Promise(resolve => {
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setTimeout(() => {
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this.bacon = 3;
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resolve();
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}, 100);
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});
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});
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var obj = { bacon: 0 };
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hooks.execPre('cook', obj, function() {
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assert.equal(3, obj.bacon);
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});
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```
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## post hooks
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acquit:ignore:end
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#### It runs without any hooks specified
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```javascript
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hooks.execPost('cook', null, [1], function(error, eggs) {
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assert.ifError(error);
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assert.equal(1, eggs);
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done();
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});
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```
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#### It executes with parameters passed in
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```javascript
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hooks.post('cook', function(eggs, bacon, callback) {
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assert.equal(1, eggs);
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assert.equal(2, bacon);
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callback();
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});
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hooks.execPost('cook', null, [1, 2], function(error, eggs, bacon) {
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assert.ifError(error);
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assert.equal(1, eggs);
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assert.equal(2, bacon);
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});
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```
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#### It can use synchronous post hooks
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```javascript
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var execed = {};
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hooks.post('cook', function(eggs, bacon) {
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execed.first = true;
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assert.equal(1, eggs);
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assert.equal(2, bacon);
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});
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hooks.post('cook', function(eggs, bacon, callback) {
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execed.second = true;
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assert.equal(1, eggs);
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assert.equal(2, bacon);
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callback();
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});
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hooks.execPost('cook', null, [1, 2], function(error, eggs, bacon) {
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assert.ifError(error);
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assert.equal(2, Object.keys(execed).length);
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assert.ok(execed.first);
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assert.ok(execed.second);
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assert.equal(1, eggs);
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assert.equal(2, bacon);
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});
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```
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#### It supports returning a promise
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You can also return a promise from your post hooks instead of calling
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`next()`. When the returned promise resolves, kareem will kick off the
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next middleware.
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```javascript
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hooks.post('cook', function(bacon) {
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return new Promise(resolve => {
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setTimeout(() => {
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this.bacon = 3;
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resolve();
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}, 100);
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});
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});
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var obj = { bacon: 0 };
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hooks.execPost('cook', obj, obj, function() {
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assert.equal(obj.bacon, 3);
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});
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```
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## wrap()
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acquit:ignore:end
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#### It wraps pre and post calls into one call
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```javascript
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hooks.pre('cook', true, function(next, done) {
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this.bacon = 3;
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next();
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setTimeout(function() {
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done();
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}, 5);
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});
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hooks.pre('cook', true, function(next, done) {
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next();
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var _this = this;
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setTimeout(function() {
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_this.eggs = 4;
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done();
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}, 10);
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});
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hooks.pre('cook', function(next) {
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this.waffles = false;
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next();
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});
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hooks.post('cook', function(obj) {
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obj.tofu = 'no';
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});
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var obj = { bacon: 0, eggs: 0 };
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var args = [obj];
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args.push(function(error, result) {
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assert.ifError(error);
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assert.equal(null, error);
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assert.equal(3, obj.bacon);
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assert.equal(4, obj.eggs);
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assert.equal(false, obj.waffles);
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assert.equal('no', obj.tofu);
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assert.equal(obj, result);
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});
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hooks.wrap(
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'cook',
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function(o, callback) {
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assert.equal(3, obj.bacon);
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assert.equal(4, obj.eggs);
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assert.equal(false, obj.waffles);
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assert.equal(undefined, obj.tofu);
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callback(null, o);
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},
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obj,
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args);
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```
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## createWrapper()
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#### It wraps wrap() into a callable function
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```javascript
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hooks.pre('cook', true, function(next, done) {
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this.bacon = 3;
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next();
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setTimeout(function() {
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done();
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}, 5);
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});
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hooks.pre('cook', true, function(next, done) {
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next();
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var _this = this;
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setTimeout(function() {
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_this.eggs = 4;
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done();
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}, 10);
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});
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hooks.pre('cook', function(next) {
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this.waffles = false;
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next();
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});
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hooks.post('cook', function(obj) {
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obj.tofu = 'no';
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});
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var obj = { bacon: 0, eggs: 0 };
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var cook = hooks.createWrapper(
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'cook',
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function(o, callback) {
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assert.equal(3, obj.bacon);
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assert.equal(4, obj.eggs);
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assert.equal(false, obj.waffles);
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assert.equal(undefined, obj.tofu);
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callback(null, o);
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},
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obj);
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cook(obj, function(error, result) {
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assert.ifError(error);
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assert.equal(3, obj.bacon);
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assert.equal(4, obj.eggs);
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assert.equal(false, obj.waffles);
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assert.equal('no', obj.tofu);
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assert.equal(obj, result);
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});
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```
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## clone()
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acquit:ignore:end
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#### It clones a Kareem object
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```javascript
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var k1 = new Kareem();
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k1.pre('cook', function() {});
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k1.post('cook', function() {});
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var k2 = k1.clone();
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assert.deepEqual(Array.from(k2._pres.keys()), ['cook']);
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assert.deepEqual(Array.from(k2._posts.keys()), ['cook']);
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```
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## merge()
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#### It pulls hooks from another Kareem object
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```javascript
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var k1 = new Kareem();
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var test1 = function() {};
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k1.pre('cook', test1);
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k1.post('cook', function() {});
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var k2 = new Kareem();
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var test2 = function() {};
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k2.pre('cook', test2);
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var k3 = k2.merge(k1);
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assert.equal(k3._pres.get('cook').length, 2);
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assert.equal(k3._pres.get('cook')[0].fn, test2);
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assert.equal(k3._pres.get('cook')[1].fn, test1);
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assert.equal(k3._posts.get('cook').length, 1);
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```
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