Must-Know

JavaScript

Tools and Techniques to learn for the Rithm School interview & main class

JavaScript is Weird...

https://www.destroyallsoftware.com/talks/wat

BUT it is logical!

https://medium.com/dailyjs/the-why-behind-the-wat-an-explanation-of-javascripts-weird-type-system-83b92879a8db

Repo with Quizzes

https://github.com/hueter/must-know-javascript

Topics

  1. Loops
  2. Arrays
  3. Strings
  4. Objects

Loops

Basic for Loop

var arr = [1,2,3];

for (let i = 0; i < arr.length; i++) {
  console.log(`${arr[i]} is at index ${i}`);
}

// 1 is at index 0.
// 2 is at index 1.
// 3 is at index 2.
var str = 'Woof';

for (let i = 0; i < arr.length; i++) {
  console.log(`${str[i]} is at index ${i}.`);
}

// W is at index 0.
// o is at index 1.
// o is at index 2.
// f is at index 3.
Array.prototype.forEach
var str = 'hello world';

str.split(' ').forEach(function(element, index) {
  console.log(`${arr[i]} is at index ${i}`);
});

// hello is at index 0.
// world is at index 1.

For arrays when you want to method-chain

for...of

var arr = [1,2,3];
for (let val of arr) {
  console.log(`The value is ${val}`);
}

// The value is 1
// The value is 2
// The value is 3
var str = 'OOP';
for (let char of str) {
  console.log(`The letter is "${char}".`);
}

// The letter is "O".
// The letter is "O".
// The letter is "P".

For strings and arrays when you don't care about the index.

for...in

var obj = { day1: "Matt", day2: "Elie", day3: "Joel", day4: "Michael" };

for (let key in obj) {
  console.log(`${obj[key]} teaches on ${key}.`);
}

// Matt teaches on day1.
// Elie teaches on day2.
// Joel teaches on day3.
// Michael teaches on day4.

For iterating through objects.

while loops

function isPalindrome(str) {
    let left = 0;
    let right = str.length - 1;
    
    while (left < right) {
      if (str[left] !== str[right]) {
        return false;
      }
      left++;
      right--;
    }
    
    return true;
}

For the most custom control.

Arrays

Arrays are Objects

typeof [] === 'object'

You need to use a special method to check for em:

Array.isArray()

Essential Array Methods

  1. includes
  2. indexOf
  3. push
  4. pop
  5. shift
  6. unshift
  7. splice
  8. slice
  9. join
  10. concat
  11. map
  12. filter
  13. reduce
  14. sort

Strings

Essential String Methods

  1. slice
  2. split
  3. replace
  4. indexOf
  5. includes

Also be able to use the += operator to append new values to strings.

Objects

Must Know JavaScript

By Michael Hueter

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Must Know JavaScript

Essential JavaScript Methods and Techniques for beginners, designed to help prospective students pass the Rithm School coding interview.

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