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){

    const newArr = [];
    for (let i=0; i<theArray.length; i++) {
        newArr.push(fnc(theArray[i]));
    }
    return newArr;

}

//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){

    const newArr = [];
    for (let i=0; i<theArray.length; i++) {
        if (fnc(theArray[i])) {
            newArr.push(theArray[i]);
        }
    }
    return newArr;

}

//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){

    let foundElement = null;
    for (let i=0; i<theArray.length; i++) {
        if (fnc(theArray[i])) {
            foundElement = theArray[i];
        }
    }
    return foundElement;

}

//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){

    const newArr = [];
    for (let i=theArray.length-1; i>=0; i--) {
        newArr.push(theArray[i]);
    }
    return newArr;

}

//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){

    const newArr = [];
    for (let i=1; i<theArray.length; i++) {
        newArr.push(theArray[i]);
    }
    return newArr;

}

//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 flip = false;
    for (let i = 0; i< theArray.length; i++){
        if (theArray[i] > theArray[i + 1]) {
          flip = true;
          // using the swap without temp algorithm!  Ex: theArray[i] = 10, theArray[i+1] = 6
          theArray[i+1] = theArray[i+1] - theArray[i];  //Ex. 6 - 10 = -4
          theArray[i]   = theArray[i] + theArray[i+1];  //Ex.  10 + (-4) = 6
          theArray[i+1] = theArray[i] - theArray[i+1];  //Ex.  6 - (-4) = 10
        }
    }
    // flip? (flip = false, return bubbleSort(theArray)) : return(theArray); // doesn't work.
    if (flip) {
      flip = false;  // setting my check
      return sort(theArray);
    } else {
      return theArray;
    }
}