Node.js Flashcards
What is Node.js?
Node.js = a javascript runtime environment (built on googles V8 js engine). It’s used inside your Chrome browser and can be downloaded into your command line program to test out code outside the web browser.
Uses an event-driven, non-blocking I/O model that makes it lightweight and efficient. It’s also wicked fast since underneath it’s written all in C code.
Node.js’ built in package manager, npm, is the largest ecosystem of open source libraries in the world.
What is a runtime environment?
Whenever a program is in the state of being executed we call this the runtime state! Programs have access to a computers RAM, its cpu, and other system resources.
You might want to test your code to see if it works, fortunately for you most software dev programs include RTEs (run time environments) in which programmers can test their code and fix any bugs that show up.
The Google Chrome browser has RTE software inside of it called V8. Node.js is Googles RTE available outside of the browser!
What can you build using Node.js?
You can build 4 things:
* Websocket server.
* Fast file Upload client
* Ad server
* Any real-time data apps
How do you run a Node.js program?
If you were to run a Node.js program outide the browser you’d have to do two things. First make sure you have node.js downloaded on your computer.
Second type in node and the name of the program you’d like to run: $ node program. That’s it.
How is a program written for Node.js?
Writing a Node.js program is no different from writing any javascript program.
- Get the elements you need.
- Use those elements in functions or loops or whatever else.
- Set overall behavior of the web page.
How does one prompt the user for an input using Node.js?
We have two ways of prompting users for inputs (neither or which is available by default in Node.js):
* Prompt (exercise 1-9)
* Prompt.sync (exercise 10…)
Prompt-sync can be downloaded from the npm website and is my preferred method of prompting, because it’s the easiest to use. First you must require it into your progrmam, then in order to prompt users you simply use the text prompt( ) and append it to a variable name with an equal sign.
myVariable = prompt( );
What is blocking code and non-blocking code?
Blocking code (synchronous code) is code that doesn’t allow end results to be read to the screen until after the necessary files have been read, and in the process of reading the file does NOT let user do anything else.
In Blocking code you might read file from file system, set equal to contents.
Print contents.
Do something else.
Non-Blocking code (asynchronous code) is code that allows users to do whatever they want while the files are being read. Once the file has been read it will print out the necessry contents.
In Non-Blocking code you real file from file system.
Do something else (and when complete, a callback, the contents are printed)
Write a Node.js program on paper takes an input, processes the input and gives the input back inside an output.
Simple. The problem asks for three things (take an input, process it, give an output).
To take an input you have to prompt the user, to prompt the user you’ll need to require into your program the prompt-sync function not available in Node.js by default. So require into your program the needed function. Then prompt the user for an entry (precede your prompt with a message asking for what you want, let’s say we’ll ask for the users name).
Once you have the name output a console.log that includes the variable input.
Done.
What should you know about dealing with integer inputs?
Every input from a user (received by way of a prompt) is translated to a string.
If you need that string to function as an integer you’d need to translate the string into an integer. You can do this using the parseInt( ) function.
What does it mean to query a DB, and what are the methods in which these requests can be done?
Querying a companies database is requesting information from a companies database or library of information. The DB belongs to the company and resides insides their servers. You, the customer, get in touch with that information by 2 means:
Blocking: customers wait in line and get information back from the DB as it is made available to the ppl ahead of you. This requires a shut down of all customer processes till this is accomplished.
Non-Blocking: customers aren’t required to wait for others queries to be processed, AND their computers do not stall while they wait, they simply get responses as soon as they are available.
