math.js

// Basic Definitions
// Integer: a whole number that is not a fraction
// Float/Floating point: approximate value for a decimal/fraction, as calculated by a computer
// Positive number: greater than zero
// Negative: less than zero
// Non-negative: greater than or equal to zero

// NaN: the only number that is not a number
// console.log(typeof 2) => 'number'
// console.log(typeof NaN) => 'number'
// console.log(typeof 'snake') => 'string'
// console.log('building' / 'house') => NaN

// + is the addition operator but in terms of strings, it is the concatenation operator
// let start = "Hello, ";
// let introduce = "my name is ";
// let name = "E.T.";
// let expression = start + introduce + name;

// console.log(expression);

// Multiplying strings (dividing strings, subtracting strings) will not work!
// These are mathematical operations! and they do not apply to strings
// let manyCats = "cat " * 5;
// console.log(manyCats); => NaN



// let ductTapePrice = 5;
// let amountOfDuctTape = 4;
// let total = ductTapePrice * amountOfDuctTape;

// if (amountOfDuctTape >= 3) {
//     total = total - (total * 10) / 100;
// }
// console.log(total)

// console.log(`The price of ${amountOfDuctTape} duct tape rolls is ${total}`);


// PEMDAS
// Easy way to remember how to get a percentage of a number:
// - multiply the number by the percentage(number)
// - divide product by 100 (to get the percentage)
// total = total - (total * 10) / 100;
// console.log(total)


let ductTapePrice = 5;
let amountOfDuctTape = 4;
let percentage = 0.1;
let getDiscountedTotal = 1 - percentage;

let total = ductTapePrice * amountOfDuctTape;
if (amountOfDuctTape >= 3) {
    // Multiplication assignment operator:
    // - runs calculation and assigns the value at the same time for shorter code
  total *= getDiscountedTotal;
  // Line below does the same thing as the line above
//   total = total * getDiscountedTotal;
}

// console.log(total)



// Math Library
let ourPrice = 5;
let competitorPrices = [2, 3, 4, 6, 7, 8];
let compPrices = [4,5,56,67,8,89]

const comparePriceRange = (prices) => {
  let min = Math.min(...prices)
  let max = Math.max(...prices)
  let priceRange = max - min;
  return priceRange;
};
// console.log(comparePriceRange(competitorPrices));
// console.log(comparePriceRange(compPrices));

const upperLimit = 10

// console.log( Math.ceil(Math.random() * 10) )

// Math.floor() => rounds down to the nearest integer
// Math.ceil() => rounds up to the next integer
// Math.round() => rounds to the NEAREST integer(up or down)
// Math.min() => takes numbers in, returns lowest number
// Math.max() => takes numbers in, returns highest number
// Math.random() =>  returns a float between 0 and 1
// Math.abs() => returns the absolute value of a positive or negative number
// Math.trunc() => returns the integer version of the number (gets rid of everything after the decimal point)
// Math.sqrt() => returns the square root of a number
// Math.pow(x, y) => takes two numbers in, returns the value of the first argument raised to the power of the second argument

// Polya's Problem Solving Methodology: Find the Median
// 1. Understand the Problem
    // - what is a median? => middle number
    // - is it a clean data set, or are there repeating numbers?
    // - if the length of the data set is even, we take the average of the two middle numbers
// 2. Devise a Plan
// 3. Carry out the Plan
// 4. Revise for Edge Cases

const nums = [
    14, 11, 16, 15, 13, 16, 15, 17, 19, 11, 12, 14, 19, 11, 15, 17, 11, 18, 12,
    17, 12, 71, 18, 15, 12,
];
//            0   1   2   3   4
const five = [11, 12, 13, 14, 17]

const findTheMedian = (arr) => {
    let medianIndex = null
    // Sort the array from smallest to largest
    const sortedArr = arr.sort()
    // console.log(sortedArr)
    // Remove duplicates to have a clean data set
        // use a Set()?
    const unique = new Set(sortedArr)
    const uniqueArr = [...unique]
    // console.log(uniqueArr)
    // Check whether the length is odd or even
    if(uniqueArr.length % 2 !== 0){
        // If it's odd: find the value at the middle index(ex: 5 length) ex: Math.floor(5 / 2)
        medianIndex = Math.floor(uniqueArr.length / 2)
        // console.log(medianIndex)
    } else {
        // If it's even: find the middle two numbers and take the average: 6 => get average of: length divided by 2 AND length divided by 2 + 1
        // 6 => 3,4 => 3+4=7 => 7/2 => 3.5
        const firstMiddleIndex = uniqueArr.length / 2 - 1
        const secondMiddleIndex = uniqueArr.length / 2
        const realMedian = (uniqueArr[firstMiddleIndex] + uniqueArr[secondMiddleIndex]) / 2
        return realMedian
    }
    // Return that number
    return uniqueArr[medianIndex]
}
// console.log(findTheMedian(nums))
// console.log(findTheMedian(five))



const unsortedNums = [735, 123, 23, 87, 3, -2, 0, 546]

// Sort() w no callback function passed to it
// Only looks at the first value/digit in the number/string
// console.log(unsortedNums.sort())

// Function below uses a ternary, which is short hand for an if statement
// In a ternary, we evaulate the expression that comes before the question mark
// If the value is truthy, then we return what comes after the question mark
// If the value i falsy, then we return what comes after the colon
const func = (a, b) => a < b ? -1 : 1

console.log(unsortedNums.sort(func))
console.log(unsortedNums.sort((a, b) => a < b ? -1 : 1))

const func2 = (a, b) => {
    if(a < b){
        return - 1
    } else {
        return 1
    }
}

console.log(unsortedNums.sort(func2))