Install

yarn add promised-hooks# ornpm install promised-hooks --save`

Warp your Class/function/object

consthooks=require('promised-hooks');// ClassclassUser{// some method that returns a PromisesomeMethod(){ ...}}// FunctionfunctionUser(){}User.prototype.someMethod=functionsomeMethod(){ ...}// Objectconstapi={save:function(){ ...}};// Wrap them to add "pre" and "post" hooks functionalities to their methodshooks.wrap(User);hooks.wrap(api);

Add middleware

pre() method

consthooks=require('promised-hooks');classUser{// instance methodssave(){ ...}// works also with static methodsstaticotherMethod(){ ...}}hooks.wrap(User);User.pre('save',doSometingBeforeSaving);functiondoSometingBeforeSaving(){// Access the arguments passed if neededconstargs=Array.prototype.slice.apply(arguments);// the scope (this) is the original Object wrapped// return a PromisereturnnewPromise((resolve,reject)=>{// ... do some async stuff// then resolve or rejectresolve();});}

Override

User.pre('save',doSometingBeforeSaving);functiondoSometingBeforeSaving(){returnnewPromise((resolve,reject)=>{// ...resolve({__override:123});// single argument// orresolve({__override:[123,'arg2']});// multi arguments});/**     * With the above override, the User.save() method will     * receive those arguments instead of the one originally provided     */}

post() method

consthooks=require('promised-hooks');classUser{// instance methodssave(){ ...}// works also with static (prototype) methodsstaticotherMethod(){ ...}}hooks.wrap(User);// Several middleware can be added at once with an ArrayUser.post('save',[postMiddleware1,postMiddleware2]);functionpostMiddleware1(data){// data is the resolved value from the original promised method// or previous "post" hooks with an __override property// do some async stuff ...// and resolve a PromisereturnPromise.resolve();// If needed, you can override the responsereturnPromise.resolve({__override:'my new response'});}functionpostMiddleware2(data){returnnewPromise((resolve,reject)=>{// call async service...myApi.doSomething((err)=>{if(err){/* if the async fails you would then reject your promise.                 * The original response is *not* overriden                 * (see errors in "post" hook below)                 */returnreject(err);}// no errorreturnresolve();});});}

Errors in "post" hooks

// For example, if the response returned by the targeted method is:'my response'// in case there are "post" hooks error it will be converted to:{result:'my response'}

consthooks=require('promised-hooks');classUser{save(){ ...}}hooks.wrap(User);User.post('save',postMiddleware);functionpostMiddleware(){returnnewPromise((resolve,reject)=>{// call async service...myApi.doSomething((err)=>{if(err){returnreject(err);}returnresolve();});});}// Somewhere else in your codeconstuser=newUser();user.save().then((response)=>{// The save occurred without issue but// let's check for any "post" hook errorif(response[hooks.ERRORS]){// deal with errors}...});

Scope (this)

classUser{save(){}__scopeHook(targetMethod,args,hookMethod){console.log(targetMethod);// "save"console.log(args);// [123]console.log(hookMethod);// "hashPassword"// You can here return any object for the scopeif(hookMethod==='hashPassword'){return{x:'abc'};// set the scope}// If you return "undefined" the scope is not changedreturnundefined;}}hooks.wrap(User);User.pre('save',functionhashPassword(){// Check the scopeconsole.log(this);// { x: 'abc' }});// ...constuser=newUser();user.save(123).then( ...);

Example

consthooks=require('promised-hooks');classUser{save(userData){returnnewPromise((resolve,reject){// ...your logic to save a user thenresolve(response);});}// works also on static methodsstaticotherMethod(){ ...}}// Wrap the class to add hooks functionalitieshooks.wrap(User);// Hash a user password before savingUser.pre('save',(userData)=>{/**     * INFO: If you need to access the User class from this middelware     * you can not use an arrow function as the scope is lost.     * Use a normal function and *this* will be your Class    */if(typeofuserData.password!=='undefined'){userData.password=hashString(userData.password);}returnPromise.resolve();// ----------functionhashString(str){// ... logic to hash a stringreturnhashedString;}});// Let's email our newly created userUser.post('save',(response)=>{// response is what the target method returnsconstemail=response.email;// Return a method that returns a PromisereturnyourMailService.sendEmail(email);});// Create new userconstuser=newUser();// Save useruser.save({name:'John',password:'snow'}).then((response)=>{// Save success// Check if there are any errors in our "post" middlewareif(response.[hooks.ERRORS]){// deal with Post hook error}},(err)=>{// Save failed});

Credits