Q.B.R.

Front-End Code Quality @ Panaya

QBR ?

In Client side we code in ?

LET'S FOCUS ON

In shorts

     used to create interactive websites

SOME FACTS

  • Was written in 1997 over the span of 10 days by Brenden Eich
  • Intends to take us a step beyond static HTML
  • IT'S NOT JAVA
    • an implementation of ECMAScript SPEC
    • each browser implements the engine as it sees fit
  • NO COMPILER
    • oh what fun...

SO JAVASCRIPT

  • lacks conformity between browsers
  • has no compiler to help us
  • full of "gotchas" that silently introduce bugs
  • Is not java... yet most programmers code like it is...

EXAMPLES

DAMN BROwSER

(function() {

   var a = "initial";
   if(a) {
       function f() { console.log("1") };
   } else {
       function f() { console.log("2") };
   }
   f();

})()

What would be printed

1 ?

2 ?

Internet Explorer

 

1

Chrome

 

 

2

Opera

 

MORE TO FEAR FROM

console.log(typeof greet);
greet();

var greet = function() {
   alert("hello!");
}
console.log(typeof greet);
greet();

function greet() {
   alert("hello!");
}

VS.

EQUALITY using == operatrtor

> 0 == false
    true
> 1 == true
    true
> 2 == true
    false
> 2 ? true : false
    true // because 2 !== 0
'' == '0'           // false
0 == ''             // true
0 == '0'            // true

false == 'false'    // false
false == '0'        // true

false == undefined  // false
false == null       // false
null == undefined   // true

' \t\r\n ' == 0     // true

DO YOU WANT TO REMEMBER THIS ?

'USE STRICT' !!!!!!!!!!!!!

if(undefined = "foo") {
    ...
}
//OH NO YOU DIDN'T!!

WE JUST RAN OVER "undefined" !!!

IE8

And So MANY MORE...

USE A "LINTER" :)

STATIC CODE ANALYSIS

 

"Lint" tools read your source code and look for common mistakes...

 

 

 

It will not make you a better coder ;)

 

(function() {
   var a = "initial";
   if(a) {
       function f() { console.log("1") };
   } else {
       function f() { console.log("2") };
   }
   f();
})()

LINT WILL GENERATE AN ERROR DURING BUILD

 "NO INNER FUNCTION DECLARATION" 

CONTENDERS

  • JS-LINT
  • JS-HINT
  • Closure Linter

WINNER: ES-LINT

TREND

SO WHY ESLINT

  • It's more flexible (~140 Rules, all can be turned off)
    • We are currently monitoring ~40
  • It's blazing fast
  • It's actively maintained and developed
  • AND IT'S EXTENSIBLE
    • Soon - angularJS rules !

SHOW ME THE MONEY

FORMALITIES

  • You can find our list of rules: *HERE*
  • You can find HOWTO's: *HERE*

Currently - during "Compile" stage

  • LINT is turned on as warnings

From "Day after 10.2"

  • LINT will FAIL THE BUILD

I am sending list of errors every Sunday to TL

Thank you

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