Code quality.

Why code quality?

Development team• Velocity

Product

• Bugs count• Time to fix• Performance• Security

Software Engineer

• Personal comfort• Motivation

Why it matters?

Average mood

understandabilityis what we need.

What we can do?

• Write better new code

• Improve existing code

print(“Hello World!”)cut.

do not increase.

Program size

• Function size

• Class size

• File size

• Package size

cut.do not increase.

Code style

style #1

var result = [];

for (var i = 0; i < l; i += 1) {

if (i % 2) {

result.push(data[i]);

}

}

style #2

data.filter(filters.modal)

Unclear responsibility

function hakuna_matata(a, b, next) {

if (!b) {

return a;

}

if (!a && !next) {

return b;

}

return “Hakuna matata!”;

}

Architectural issues

Why it happens?qualification, dude.

We don’t do what is needed!

What was estimated

What we wanna built

What we have done

Manage your time.

Improve existing code.80 - 20

Pareto principle.

Measure!

Lines of code - LOC

for (i = 0; i < 100; i++) printf("hello"); /* How many lines of code is this? */

Logical lines of code - LLOC

/* Now how many lines of code is this? */

for (i = 0; i < 100; i++)

{

printf("hello");

}

Number of lines of code

Simple code

function sayHello() {

print(“Hello”)

}

Difficult code

function say(message) {

if (!message) {

return false;

}

if (message == “Hello”) {

print(“Hello World!”);

return;

}

message && print(message);

}

Cyclomatic complexity

Difficult code

function say(message) {

if (!message) {

return false;

}

if (message == “Hello”) {

print(“Hello World!”)

return;

}

print(message)

}

✓ 3 tests passed

100% coverage

say() == false

say(“Hello”) == “Hello World!”

say(“Text”) && output == “Text”

Code coverage

Other metrics• Cohesion• Coupling• Connascence• DSQI• Maintainability index• Comment density• Halstead complexity• Number of classes• Number of parameters• Number of dependencies• Execution time• Load time…

SonarQube

Plato

Code analysis platforms

node install complexity-report

LLOC Complexity Density

5440 703 13 %

5864 1448 25 %

11739 2132 18 %

965 275 28 %

Metrics example

Metrics example #2

git log --name-only -- *.js | grep .js | sort | uniq -c | sort -n

git diff --stat `git rev-list HEAD | tail -n 1` HEAD | grep .js | awk '{ print $3 " "$4 " "

$1}' | sort -n

Version control system

Let’s make our life better!that’s all.

Average mood