Interviewing for Frontend Engineers

Inital phone screen

Current job satisfaction
What the next place offers, apply with intentionality
- Engineering culture
- What would make you happy

difference between const let var
- The scope is global when a var variable is declared outside a function.
- var is function scoped when it is declared within a function.
- This means that we can do this within the same scope and won’t get an error:
```
var greeter = "hey hi";
var greeter = "say Hello instead";
  
var greeter = "hey hi";
greeter = "say Hello instead";
```
var variables can be re-declared and updated Hoisting of var
var variables are hoisted to the top of their scope and initialized with a value of undefined.
What is hoisting?
- Hoisting is a JavaScript mechanism where variables and function declarations are moved to the top of their scope before code execution.
let can be updated but not re-declared.
let declarations are hoisted to the top.
let is not initialized
- try to use a let variable before declaration get a Reference Error
const cannot be updated or re-declared
const object cannot be updated
- properties of objects can be updatedconst object as this:
- cannot do this:

const greeting = {
  words: "Hello",
  number: "five"
}

greeting.message = "say Hello instead";

const declarations are hoisted to the top but are not initialized
Explain prototypical inheritance
- A prototype is a working object instance. Objects inherit directly from other objects.
What is this
- The scope you’re in but if it is not locally defined, this refers to the global object
What is the data structure of the DOM
- The DOM is a tree
What is a stack and a queue?
- Data structures
- stack
  - Last in first out
  - use an array pop(), push()
- queue
  - first in first out
- Image loaded on page
  - onLoad callback will be fired
- What is call() and apply()
  - Ways of changing the scope of the calling function
    - call: series of arguments
    - apply: array of arguments
- Event delegation
  - Have one event listener at the top when you click it bubbles up to the parent
  - Event listeners are expensive (performance)
- What is a worker
  - Worker is a thing in a browser to offload an expensive operation

The average case for how long a function will take to run

function search(arr, num) {
for (let i = 0; i < arr.length; i++) {
  if(arr[i] === num) {
    return true;
  }
}
return false;
}

function search(arr, num) {
  for (let i = 0; i < arr.length; i++) {
    if(arr[i] === num) {
      return true;
    }
  }
  return false;
}

1 for loop, return early
- element at index 0 is best case
- will return instantly
- size of inputs doesn’t matter

💡Tip:

Big-O, count the loops

Ask questions
- not too many
talk out your solution
- especially if stuck
  - need to let interviewer know how you’re thinking
get comfortable with environment

createDocumentFragment() for appending more than once
- constantly rendering to the DOM with multiple appendChild() has perfomance implications
extracting the target event from the DOM and using childNodeRemove is [Event Delegation]

function reverse(str) {
  return str.split('').reverse().join();
}