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Rapid ES6 Training

An ES6 compatibility chart: kangax.github.io/compat_table/es6

New ES6 Syntax

let, const, and block scoping

• let: Not hoisting, we make sure the variable exist before using it
• Block scoping: We can redefine a variable within a block and that variable wil dissapear outside the block
• const: When we use the const keyword to define a variable we MUST initialize it

With letand const anything declared inside the block, STAYS in the block

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Instructions

1. Clone the repository to your local development environment https://github.com/simple-statistics/simple-statistics
2. git checkout to tag v7.7.2

Description of the bug

The mean() function does not raise an error for null values in sample, nor is there a note in the documentation specifying this.

Here's an example of where I realized this:

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Describe the bug

Creating a duration using a decimal hour then using toFormat produces an incorrect result

The inputs we've seen wrong so far are 2.4 and 5.3

To Reproduce

luxon.Duration.fromObject({hour: 2.4}).toFormat('hh:mm') returns "02:23"
luxon.Duration.fromObject({hour: 5.3}).toFormat('hh:mm') returns "05:17"

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Leadership and Communication Skills for Software Engineers

Communication is where leadership leaves and breaths

Effective communication is the most critical skill a leader can posses when working with others.

The leader is the message.

First Steps

• Establish the team way of work ahead of time.
• Set and clarify goals.

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An ES6 compatibility chart

New ES6 Syntax

let, const and block scoping

• let: Not hoisting, we make sure the variable exist before using it.
• Block scoping: We can redefine a variable within a block and that variable will disappear outside the block.
• const: When we use this keyword to define a variable we MUST initialize it.

With letand const, anything declared inside the block STAYS in the block.

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Rule 1 Let your database do what databases are good at, instead of doing it in Ruby.

Rule 2 Write efficient and chainable Scopes

1. Return an ActiveRecord::Relation (i.e. don't trigger that query)
2. Filter data in the database (not in Ruby)
3. Sort in the database (not in Ruby)
4. Leave ordering out of scopes (or capture in a dedicated scope)

Rule 3 Reduce calls to the Database

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Scalable and Modular Architecture for CSS

Categorization

• Every style we write serves one of these purposes wheter we're aware of it or not
• Isolating code allows for easier, reuse, testing and debugging
• Categorizing reveals patterns; easier to identify when things break the pattern

Base styles

• Reset
• Normalize

Layout styles

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Part 1: Adopt the Right Mindsets

Focus on High-Leverage Activities

How should we decide what actually to work on in order to more effectively achieve our goals? Assess the activities' leverage:

Leverage =  (Impact Produce) / (Time Invested)

Another way of thinking about leverage is the commonly-mentioned Pare- to principle, or 80–20 rule—the notion that for many activities, 80% of the im- pact comes from 20% of the work.

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Docker Architecture and Theory

The Big Picture

Container: Isolated area of an OS wioth resource usage limits applied. To build containers we use low level kernel controls: namespaces and control groups.

We use the CLI docker container run which makes a call to the appropiate Docker API containers/create

Kernel Internals

We use two main building blocks when creating containers: Namespaces and Control Groups, both of them are Linux kernel primitives.

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Common Object Patterns

Function Arguments

Arguments aren't required like .NET languages, like all variables in JavaScript arguments are untyped.

Argument Object

Available in all functions, like an array, but not really and array (cannot sort or filter)

argument[0]