code-examples

Equal Sides Of An Array

A code wars kata that find the index where the sum of the numbers on the left are equal to the sum of the numbers on the right.

function findEvenIndex(array) {
    const sum = array.reduce((x, y) => x + y, 0);
    let accumulator = 0;
    for (let i = 0; i <= array.length; i++) {
        if (accumulator == (sum - array[i]) / 2) {
            return i
        }
        accumulator += array[i];
    }
    return -1
}

/** The reduce method is used to find the sum of the array
 * The next pass of the array is accumulated as it iterates.
 * The condition is met when the accumulator is half of the sum 
 * after the present iteration value is taken away from the sum
 * The final return of -1 is if the condition is never met
 */

findEvenIndex([1,2,3,4,3,2,1]) // returns 3
findEvenIndex([1,100,50,-51,1,1])// returns 1
findEvenIndex([1,2,3,4,5,6]) // returns -1
findEvenIndex([20,10,30,10,10,15,35]) // returns 3

Calculate with functions

function zero(num)     { return num ? num(0) : 0 }
function one(num)      { return num ? num(1) : 1 }
function two(num)      { return num ? num(2) : 2 }
function three(num)    { return num ? num(3) : 3 }
function four(num)     { return num ? num(4) : 4 }
function five(num)     { return num ? num(5) : 5 }
function six(num)      { return num ? num(6) : 6 }
function seven(num)    { return num ? num(7) : 7 }
function eight(num)    { return num ? num(8) : 8 }
function nine(num)     { return num ? num(9) : 9 }

function plus(x)        { return function(y) { return y + x }}
function minus(x)       { return function(y) { return y - x }}
function times(x)       { return function(y) { return y * x }}
function dividedBy(x)   { return function(y) { return y / x }}

/**
 * A Codewars kata that uses functions to calculate 2 numbers.
 * The right operand returns a number to the operator which in turn returns a 
 * curried function to the left operand.
 * While this example is not DRY, and I could have tried putting the numbers into an array
 * I think it is more readable this way.
 */

seven(times(five())); // returns 35
four(plus(nine())); // returns 13
eight(minus(three())); // returns 5
six(dividedBy(two())); // returns 3

Password Validation

function validatePIN (pin) {
    return /^\d\d\d\d$/.test(pin) || /^\d\d\d\d\d\d$/.test(pin)
}

Extract the domain name from a URL

    function domainName(url) {
        const out = url.replace(/(www.)|(https)|(http)|(:\/\/)/g, '').split('.')
        return out[0]
    }

Exes and Ohs

function XO(str) {
    let result = str
        .toLowerCase()
        .split('')
        .reduce((x, y) => {
            if (y == 'x') {
                x++
            }
            if (y == 'o') {
                x--
            }
            return x
        }, 0)

    return result == 0 ? true : false
}

XO("ooxx") => true
XO("xooxx") => false
XO("ooxXm") => true
XO("zpzpzpp") => true // when no 'x' and 'o' is present should return true
XO("zzoo") => false

Square Every Digit

Take every digit and square it and then join together

function squareDigits(num){
  const str = num
     .toString()
     .split('')
     .map(x => (x * x)) 
     .join('')
     
     const result = parseInt(str, 10)
     
     return result    
     }

     squareDigits(9119) // returns 811181

Highest and Lowest

A code wars kata. The function returns the highest and lowest number in a given string.

function highAndLow(numbers){
const array = numbers.split(' ')
  const max = Math.max(...array);
  const min = Math.min(...array);
  return max + " " + min;

highAndLow("1 2 3 4 5"); // return "5 1"
highAndLow("1 2 -3 4 5"); // return "5 -3"
highAndLow("1 9 3 4 -5"); // return "9 -5"

The Longest

Take 2 strings s1 and s2 including only letters from a to z. Return a new sorted string, the longest possible, containing distinct letters.

function longest(s1, s2) {
  const result = (s1 + s2)
    .split('')
    .filter((el, pos, arr) => arr.indexOf(el) == pos)
    .sort()
    .join('')

  return result
}

longest("loopingisfunbutdangerous", "lessdangerousthancoding") //returns "abcdefghilnoprstu"
longest("inmanylanguages", "theresapairoffunctions") //returns "acefghilmnoprstuy"

Return the nth triangular number

def triangular( n )
  n > 0 ? (1..n).reduce(:+) : 0
end