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NodeJS Interview

memorize.ai (lvl 286)

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node's callback pattern

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Mar 1, 2020

Cards (36)

Section 1

(36 cards)

node's callback pattern

Front

do_something(param1, param2, ..., paramN, function (err, results) { ... } );

Back

fs.readdir(file, callback)

Front

returns all items in the given folder except for "." and ".."

Back

create a module that prints out "Hello World"

Front

exports.hello_world = function () { console.log("Hello World"); }

Back

what is the global object in NodeJS

Front

similar to window object for JS in the browser, anything attached to the global object is available anywhere in your node app

Back

can you chain multiple .pipe()'s together

Front

yes

Back

where does npm install module packages

Front

the node_mpdules subdirectory of your project

Back

four core REST operations

Front

get, put, post, delete

Back

what does the module variable of each module contain

Front

information such as the filename of the current module, its child modules, its parent modules, etc

Back

what defines NodeJS

Front

non-blocking IO and asynchronous programming

Back

what is the most powerful and awesome feature of the Node.js module system

Front

in a situation where you have a main widget and a special widget, each with their own node_modules/ dir, requiring special widget will import it's node_modules/, not the main widget's. version control.

Back

PUT /albums.json

Front

The HTTP request body contains the JSON with the data for the new album.

Back

are for loops and async callbacks compatible?

Front

not really, need to use recursion instead

Back

parse this url: /albums/italy2012.json?page=1&page_size=20

Front

url.parse(req.url, true) //{ search: '?page=1&page_size=20', query: { page: '1', page_size: '20' }, pathname: '/albums/italy2012.json', path: '/albums/italy2012.json?page=1&page_size=20', href: '/albums/italy2012.json?page=1&page_size=20' }

Back

npm link

Front

tells npm to put a link to the album-manager package in the local machine's default public package repo

Back

npm update

Front

updates the modules from package.json

Back

aync.auto function

Front

lets you mix ordered and unordered functions together into one powerful sequence of functions

Back

write a synchronous version of a script to read a file

Front

var fs = require('fs'); var handle = fs.openSync('info.txt', 'r'); var buf = new Buffer(100000); var read = fs.readSync(handle, buf, 0, 10000, null); console.log(buf.toString('utf-8', 0, read)); fs.closeSync(handle);

Back

how do you handle a situation where you are losing the this pointer?

Front

enclose the function within a function, then assign self to this (var self = this;). this preserves this via closures in function scope

Back

the async node module

Front

provides an intuitive way to structure and organize asynchronous calls

Back

install sql with npm

Front

npm install sql

Back

exports object

Front

a special object created by the Node module system in every file you create and is returned as the value of the require function when you include the module

Back

How to load script to Node REPL?

Front

.load foo.js from within Node REPL

Back

the pattern for using streams

Front

.on(event_name, function (param) { ... });

Back

console.assert(cond, message)

Front

if cond evaluates to false, throw an AssertionFailure exception

Back

If functions return immediately, why doesn't the node process exit immediately after the function has returned?

Front

Node operates on an event queue; if there are pending events awaiting a response, it doesn't exit until your code has finished executing AND there are no events left in the queue

Back

.pipe()

Front

a function that takes a readable source stream and outputs to a writable stream

Back

async.forEachSeries

Front

iterates over every element in the provided array, calling the given function for each

Back

write a function to asynchronously open and read a file

Front

fs.open( 'into.txt', 'r', function (err, handle) { var buf = new Buffer(100000); fs.read( handle, buf, 0, 100000, null, function (err, length) { console.log(buf.toString('utf-8', 0, length)); fs.close(handle, function () { }); } ); });

Back

what are streams

Front

streams are a powerful way to transfer large amounts of data in Node while maintaining the asynchronous, nonblocking nature of the sytem

Back

npm install

Front

installs the modules from package.json

Back

process.nextTick()

Front

defers the execution of an action till the next pass around the event loop, it is executed on a whole new stack. useful when preventing cpu intensive tasks from blocking other processes

Back

what is the require function

Front

a way to include additional functionality to node programs var fs = require('fs'); // includes file system module

Back

GET /albums/italy2012.json

Front

the request returns this album

Back

update an installed package

Front

npm update mysql (npm update to update all)

Back

write a function that handles errors in callbacks

Front

fs.open( 'info.txt', 'r', function (err, handle) { if (err) { console.log("ERROR: " + err.code + " (" + err.message ")"); return; } else { // success! continue working here } );

Back

search for sql modules

Front

npm search sql

Back