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Application Design Notes

Don’t be afraid to write your own code, but be absolutely sure you need to Don't reinvent the wheel Learn more about your libraries and take full advantage  Date time calculation is hard ( leap second ,  leap year ), use trusted library  js-joda ,  momentJs ,  joda (java) Simple is better than perfect (nearly) every time If you can deliver a sub-optimal solution (that solves the problem but has known limitation) in a week instead of a full featured one in a month DO, IT Simple system are Easy to reason about  Easy to debug Easy to refactor Easy to learn Simple doesn't mean you skip good engineering, but you can use duct tape. Build things the right way from the start, refactoring is hard and expensive Security Manage and store passwords securely Telemetry Common retrofitting "grunt work" Internationalization + localization Web Content Accessibility Factoring and styling HTML UI Adding unit test to an existing codebase LOG LOG LOG Log, but do it right We spend lot of t
Recent posts

CSS Specificity

    Many time different CSS rules overlap on one or more element. And some people always get confuse about, which rule will take higher priority then other and why? CSS Specificity is the answer of all these kind of questions. As the name suggest, the CSS rule which is more specific to the element will take higher priority then other. Means something like “#some_id{}” will always take higher priority then “*{}” universal selector.  And if duplicate rules are define then the last rule will be applied to the element. The following list of selectors is by increasing specificity: Type selector (e.g., div) and pseudo-elements in selector (e.g., :after) Class selectors (e.g., .some_class), attributes selectors (e.g., [type=”radio”]) and pseudo-class selector (e.g., :hover) Id selectors (e.g., #some_id) ID takes higher priority then Class, Type and Universal selector (Note: Universal selector has no effect on specificity, see below special conditions).  If d

How to store user password at server!!!

Trick is, you should never store user password… never ever. Now the real question is, then how to authenticate and authorize the user with password. And answer is when user enter the password, we should encrypt the password and store the hints. So next time when user enter the password we follow the same process and compare hints, if both hints are same then password is matched, else it is wrong password. Next question will be, what kind of hints, and how to generate these hints. In simple term hints are the obfuscated and fragmented form of user password. And very important part is hints generation process, which have to be collision resistant , means there will be very less possibility to find the data which generate same hints (like Cryptographic hashing functions ). Below is the simple checklist of password hashing and storing, which you should always keep in mind. PS You're Probably Storing Passwords Incorrectly Storing Passwords - done rig

ERROR: Ignored call to 'alert()'. The document is sandboxed, and the 'allow-modals' keyword is not set.

Recently I found this issue while writing code snippet in "JSFiddle". And after searching, found this was happening because of new feature added in "Chrome 46+". But at the same time Chrome doesn't have support for "allow-modals" property in "sandbox" attribute. Chromium issue for above behavior: To make it work you have to add "allow-scripts allow-modals" in "sandbox" attribute, and use "window.alert" instead of "alert". <!-- Sandbox frame will execute javascript and show modal dialogs --> <iframe sandbox="allow-scripts allow-modals" src="iframe.html"> </iframe> Feature added: Block modal dialog inside a sandboxed iframe. Link: Feature working Demo page:

JavaScript: Next Unique ID Function

Unique ID generation is used in JavaScript application in many places. For example giving the unique id to DOM element or may be using it to some data structure for storing in memory, where it can be use latter. Most of the implementation I see is just defining the integer and increasing it on every call. But it is potentially candidate to integer overflow issue, which can cause errors in many edge case scenario. var nextUid = (function(){ var idCounter = 0; //integer counter return function (prefix) { //counter increment on every call, and it can run into integer overflow issue var id = ++idCounter; return String(prefix == null ? '' : prefix) + id; } })(); When I was reading through AngularJS source code, found this really good implementation of unique ID generation. Below is the extracted and updated version of the same, so you can use it independently. /** A consistent way of creating unique IDs in angular. The ID is a seque

JavaScript: Utility function to default function in parameters

Recently I came across a interesting discussion on  reddit . And that was about a utility function which will give you flexibility to define default function in parameters. I found it very interesting, so wrote one for me. /* in param: defaultArg1, defaultArg2, .... function return : function */ var defaultParams = function(){ var args = arguments, len = args.length, fn = args[--len], defaultArg = []; if(typeof fn !== 'function'){ throw new Error('invalid arguments'); } while(len--){ defaultArg[len] = args[len]; } return function(){ var args = arguments, fnlen = fn.length, params = []; while(fnlen--){ params[fnlen] = args[fnlen] == null ? defaultArg[fnlen] : args[fnlen]; } return fn.apply(this, params); } } //how to use var alert_my_age = defaultParams(21, function(age) { console.log(age); }) alert_my_age() //#=> Alerts 21 alert_my_age(45) //#=> Alerts 45

JavaScript: Light weight wrapper class for window.localStorage

Recently I wrote a small wrapper class around the window.localStorage with useful functionality apart from normal get/set value. For example Accessors for JSON/Boolean/Number, Event registering for type create/update/remove/clear events API functions LS.set(key, value) LS.setJson(key, jsonObject) LS. remove (key) LS. clear () LS.get(key) : String LS.getJson(key) : JsonObject LS.getNumber(key) : Int LS.getBoolean(key) : Boolean //Event API LS.on( event , listenerFunction, scope) : function //this return function can be used for unregistering from event //different type and listeners callback param events type : ' create ' listenerFunction callback param : key, value events type : ' update ' listenerFunction callback param : key, newValue, oldValue events type : ' remove ' listenerFunction callback param : key events type : ' clear ' listenerFunction callback param : //remove all the registered event for