array-functions.js

//in the function map, create a new array and store in a variable
//loop theArray and call the fnc for each thing in the array,
//     passing in the item from the current loop into the call to fnc
//add the returned value from fnc to the new array
//return the new array
export function map(theArray, fnc){
  let newArray = [];
  theArray.forEach((index) => {
    newArray.push(fnc(index));
  })
  return newArray;
}

//create a new array
//loop theArray and call the fnc for each thing in the array,
//     passing in the item from the current loop
//fnc will return true or false, if true add the item to the new array else do not
//return the new array
export function filter(theArray, fnc){
  let newArray = [];
  theArray.forEach((item)=> {
    if(fnc(item)) {
      newArray.push(item);
    }
  })
  return newArray;
}


//loop theArray and call the fnc for each thing in the array,
//     passing in the item from the current loop
//fnc will return true or false, if true return the item
//return null
export function find(theArray, fnc){
  for(let i = 0; i < theArray.length; i++) {
    if (fnc(theArray[i])){
      return theArray[i];
    }
  }
}


//return the last item in theArray
export function findLast(theArray){
  return theArray[theArray.length - 1];
}

//return the first element of the array
export function head(theArray){
  return theArray[0];
}

//create a new array
//loop theArray in reverse order
//add the item from each loop to the new array
//return the new array
export function reverse(theArray){
  let tempArray = [];
  for (var i = theArray.length - 1 ; i >= 0; i--) {
    tempArray.push(theArray[i]);
  }
  return tempArray;
}

//create a new array
//loop theArray
//add the item from each loop to the new array except the first item
//return the new array
export function tail(theArray){
  let tempArray = [];
  for (var i = 1; i < theArray.length; i++) {
    tempArray.push(theArray[i]);
  }
  return tempArray;
}

//implement the most basic sorting algorithm there is
//assume the array will always have numbers
//use a while loop to constantly loop theArray until it is sorted
//use a for loop to loop theArray
//look at the current item and the next item, compare them
//if the items are out of order, swap them
//initialize a variable that indicates if a swap had to be done, set it to false
//if a swap is done set it to true
//after each for loop check the variable, if true, continue the while loop
//if false return theArray
export function sort(theArray){
  let newArray = theArray;
  let swapped;
  do {
    swapped = false;
    for (var i = 0; i < newArray.length; i++) {
      if (newArray[i] > newArray[i + 1]) {
        let temp = newArray[i];
        newArray[i] = newArray[i + 1];
        newArray[i + 1] = temp;
        swapped = true;
      }
    }
  } while (swapped === true)
  return newArray;
}