This is a living and breathing document and generally works as a agenda for my interviews. The updation are intended to be frequent. Apart from the language section the document is intended to be as language, hence framework, agnositic as possible.
- General Questions
- Design Pattern Questions
- JS Code examples
- JS Specific Questions
- Database Specific Questions
- Operating System Specific Questions
- Web Services Specific Questions * Common Server Response Codes
- Network Specific Questions
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-
What did you learn yesterday/this week? Or most recently?
-
How do you go about testing your JS code?
-
What are the common libraries or frameworks you use for end to end developemnet? :
ideally should include server framework, front end framework, db orm, db manipulations , deployment tech, cache handling, testing, logging and error reporting. -
When do you optimize your code? What kind of process you follow for it? :
should include some kind of perf monitorining. -
What's the most recent big problem faced on your current projects and how did you solve it? Should be in last 2 weeks.
-
What do you consider one of your failures in your current job?
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What is the output here? Why?
function logIt(){
console.log(text);
var text = 'inside';
};
logIt();
Output will be undefined. Variable declarations are hoisted only not the assignemts.
<button id="btn-0">Button 1</button>
<button id="btn-1">Button 2</button>
<button id="btn-2">Button 3</button>
<script type="text/javascript">
const prizes = ['A Unicorn!', 'A Hug!', 'Fresh Laundry!'];
for (var btnNum = 0; btnNum < prizes.length; btnNum++) {
// For each of our buttons, when the user clicks it...
document.getElementById(`btn-${btnNum}`).onclick = () => {
// Tell her what she's won!
alert(prizes[btnNum]);
};
}
</script>
The loop does not stop until btnNum = 3. The inner function gets the value of btnNum 3 always as the btnNumber is not passed to the onClick function. It will always alert(prize[3]) hence undefined
- What does the code snippet prints?
(function() {
var a = (b = 3);
})();
console.log("a defined? " + (typeof a !== "undefined"));
console.log("b defined? " + (typeof b !== "undefined"));Output:
//a defined? false
//b defined? true
//b = 3;
//var a = b;
- Write the function which prints the following output.
console.log(mul(2)(3)(4)); // output : 24
console.log(mul(4)(3)(4)); // output : 48Below is code followed by an explanation how it works:
function mul(x) {
return function(y) {
// anonymous function
return function(z) {
// anonymous function
return x * y * z;
};
};
}- What is the difference between the following code samples?
var foo = function() {
// Some code
};
function bar() {
// Some code
}- What will the following code output?
const arr = [10, 12, 15, 21];
for (var i = 0; i < arr.length; i++) {
setTimeout(function() {
console.log("Index: " + i + ", element: " + arr[i]);
}, 3000);
}It outputs Index : 4 , element : undefined.
- How would you change the above snippet to make it print logically?
- ES6 way:
const arr = [10, 12, 15, 21];
for (let i = 0; i < arr.length; i++) {
// using the ES6 let syntax, it creates a new binding
// every single time the function is called
// read more here: http://exploringjs.com/es6/ch_variables.html#sec_let-const-loop-heads
setTimeout(function() {
console.log("The index of this number is: " + i);
}, 3000);
}- other way
const arr = [10, 12, 15, 21];
for (var i = 0; i < arr.length; i++) {
// pass in the variable i so that each function
// has access to the correct index
setTimeout(
(function(i_local) {
return function() {
console.log("The index of this number is: " + i_local);
};
})(i),
3000
);
}- Write the function which prints the following output.
var addSix = createBase(6);
addSix(10); // returns 16
addSix(21); // returns 27- The primitive types are stored as the value themselves, unlike objects, which are stored as a reference. This has implications when performing equality checks.
"dog" === "dog"; // true
14 === 14; // true
{} === {}; // false
[] === []; // false
(function () {}) === (function () {}); // false
- A function is a special type of object, with some special properties, such as constructor and call.
const foo = function (baz) {};
foo.name; // "foo"
foo.length; // 1
And just like a normal objects, you can add new properties to the object:
foo.bar = "baz";
foo.bar; // "baz"
This makes functions a first-class citizen, because it can be passed around, as arguments into other functions, just like any other objects could.
Methods: A method is a object property that also happens to be a function.
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- Describe two good uses - and pratices - for callback usage.
- what is mixin ? : Diamond Problem : make a seperate class for the things that you need in other classes.
- How to defer javascript loading on the frontend?
- What is the default return value of js fuction when no return has been explicitly defined.
- What is
self? Why we need it seperately fromthis? - What is annonymous functions and why we need them? (deceration at run time or complie time)
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- What is the use case of noSQL and SQL databases?
- Have you worked with an in-memory db? What are your common concerns there?
- Have you worked on production deployed MongoDb? _ Have you managed a replica set? _
- Do you know PostgreSQL? * How do you improve Resource Consumption?
- SQL Server * How would you migrate from SQL Server to PostgreSQL or MySQL?
- Do you know How to 'hack', build a cluster, improve performance, implement cache, pooling or compile those services from source?
- Are you familiar with NoSQL databases?
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- What happens between the time you enter a URL in your browser until you see the page that you requested?
- How does the 3-way TCP handshake occur when you request a page from a server?
- What are the contents of an HTTP request header? Response header?
- What is the difference between HTTP and HTTPS?
- How would you design a URL shortener similar to bit.ly?
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- Have you created or managed some web service?
- What web service protocals do you know?
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- Linux/Unix/MacOS _ How would you install, configure and handle services such nginx, apache, squid, samba, etc..? _ What do you know about kernel tuning? _ What do you know about virtualization? _ What is the difference between threads and processes?
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- What are the 7 layers of the OSI model?
- What are some advantages of CDNs? Disadvantages?
- What is a reverse proxy?
- What ports do the following use? _ HTTP _ HTTPS * SSH
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SELECT subQuery.condition, max(subQuery.severity) as severity,
json_agg(json_build_object(
'vulnerability', subQuery.vulnerability,
'asset', subQuery.asset,
'severity', subQuery.severity
)) AS asset
FROM (
SELECT author.genre, author.name,
books.title, author.title
FROM author inner join books
on books.if = author.book-id
)subQuery
GROUP BY subQuery.genre
author
genre
name
book-id(fk)
books
id
title
author(fk)
class Musician(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) instrument = models.CharField(max_length=100)
class Album(models.Model): artist = models.ForeignKey(Musician, on_delete=models.CASCADE) name = models.CharField(max_length=100) release_date = models.DateField() num_stars = models.IntegerField()