No, you can’t. I’ve got an example for you:

var a={},
    b={key:'b'},
    c={key:'c'};a[b]=123;
a[c]=456;console.log(a[b]);
console.log(a[c]);

Output of both console.log statements will be 456. To understand why it it so, we should use base Object method toString() on both objects. We will see following output:

> b.toString();
< "[object Object]"
> c.toString();
< "[object Object]"

So when you use object as a key of another object it internally converts to string with value [object Object]. So this is all equal calls:

a[b] === a[c] === a[{}] === a["[object Object]"]

But if you still want to use object as a key, you should use ES6 Maps.

Recently I’ve dived into ECMA-262 (9th Edition / June 2018) specification and in this article I will try to explain variable hoisting using LexicalEnvironment and VariableEnvironment. This article mainly summarise answers to several StackOverflow questions and my understanding of the specification.

The difference between var and let declarations is scoping. var is scoped to the nearest function block and let is scoped to the nearest enclosing block, which can be smaller than a function block. Both are global if outside any block. Also, variables declared with let are not accessible before they are declared in their enclosing block.

Let’s review…

Story about inferential statistics project

This story won’t be a step by step guide to becoming Data Scientist, because I have no idea what should I do after completing following project. So I decide to write a story each time I have some accomplishments on my way.

Something about my background: I’m full-stack software developer in banking sector, so my primary tech is Java 8, Oracle SQL and modern front-end frameworks like React/Vue. I’ve also finished bachelor’s degree in Applied Mathematics and master’s in Computer Science, so I have some math background, but I need some time to remember concepts…

When I was a student, I’ve got first acquaintance with banking sector and it was awful experience. A lot of software developers sit in narrow open space and they’ve got only one point to access Internet — laptop with mobile wi-fi. I was scared of banks since then.

Several years later I’ve got job offer from bank with high-end tech and agile development process. I was really impressed by that, as I could never imagine modern tech in such solid and conservative companies. As I see now, banks on the edge of agile and lean techniques as they should faster…

Recently, I’ve encountered interesting task. I should create proxy with apache or nginx for weblogic application. So this article will be about it.

Overall configuration is following:

worker_processes  1;error_log  logs/error.log;  
error_log  logs/error.log  notice;  
error_log  logs/error.log  info;pid        logs/nginx.pid;
events {  
    worker_connections  1024;
}
http {  
    include       mime.types;
    default_type  application/octet-stream;    sendfile        on;
    keepalive_timeout  65;    # 1
    proxy_buffer_size   128k;
    proxy_buffers   4 256k;
    proxy_busy_buffers_size   256k;    # Redirect all http to https
    server {
        listen 80;
        server_name example.com;
        # 2
        return 301 https://$server_name$request_uri;
    }    # SSL configuration
    server {
        #3
        listen 443 ssl;
        server_name example.com;        ssl_certificate           certs/example.com.cer;
        ssl_certificate_key       certs/example.com.key;…

While waiting for the project from outsource company, I’ve started to investigate information about Java Play 2 Framework. And it’s really impressive modern tool, which can be used to create amazing web applications. It also has powerful tool to create REST services.

Outsourced application has Angular.js, Gulp, Node.js on front-end and Java Play 2 Framework on the backend. So I’ve decided to learn how to retrieve information from database and pass it to JavaScript frameworks, so I’ve decide to write an application that will get data from database and convert it into json.

I’ve got several applications and I think…

This is very important question, because it take a lot of time when you met Django for first time. This guide is for setting up Django MEDIA and STATIC files for development environment and it will be more compact then official guide, though I'll give a reference to it.

Configuration of settings.py and urls.py

First you should consult official documentation and be sure that you’ve setup proper middleware classes. If you create new project with manage.pyor using PyCharm then this classes is already in there, but you should check it anyway.

Then you should specify MEDIA_ROOT and STATIC_ROOT:

STATIC_URL = '/static/'  
STATIC_ROOT = os.path.join(BASE_DIR, …

I need fast and effective method to get three count from one table for statistic on my current personal project. And then I’ve found easy and elegant way to do so:

select count(*) Total,  
       sum(case when is_approved = 't' then 1 else 0 end) PendingCount,
       sum(case when is_rejected = 't' then 1 else 0 end) RejectedCount
from project_project

You could add group by statement so this code will show you counts for groups. This code I’ve tested in PostgresSQL. I’ll try to test it with Oracle DB and will write an update.