Finding elements in first half of Javascript array

Question

I don't understand well this exercise.

arr = [1, 2, 3];
arr.indexOf(2); // 1
arr.indexOf(4); // -1 since it doesn't exist.

// Write a function to determine if an element
// is in the first half of an array.
// If an element has an odd length, round up
// when counting the first half of an array.
// For example, 1 and 2 are in the first half
// arr.
function inFirstHalf(inputArray, element) {

}

I don't got it, what does mean first half of an array?

I guess it means if indexOf returns a value that is less than half of arr.length, rounded up if length is odd (which means you'll actually have to round down, since array indexes start at 0). — RobG
– RobG, Commented Nov 4, 2015 at 2:01
Thank you @RobG, I am taking this course codecademy.com/courses/javascript-intro/8/4, I was stuck in that exercise. — ricardoorellana
– ricardoorellana, Commented Nov 4, 2015 at 2:07

user663031 · Accepted Answer · 2015-11-04 04:05:56Z

2

Look up the value in a new array created by slicing the original array in two:

arr.slice(0, Math.ceil(arr.length/2)) . indexOf(val)

answered Nov 4, 2015 at 4:05

user663031

Sign up to request clarification or add additional context in comments.

Comments

xourscode · Accepted Answer · 2015-11-04 05:21:35Z

-1

You should retrieve the length of the array arr using the length property. Now you have to check whether the element index is smaller than length and round up when length is odd.

function inFirstHalf(inputArray, element) {
    if ((inputArray.length % 2) === 0) {
        if ((inputArray.indexOf(element) + 1) <= (inputArray.length / 2)) {
            return true;
        }
    } else {
        if ((inputArray.indexOf(element) + 1) <= Math.ceil ((inputArray.length / 2))) {
            return true;
        }
    }
    return false;
}

edited Nov 4, 2015 at 5:21

answered Nov 4, 2015 at 2:14

xourscode

894 bronze badges

3 Comments

user663031 Over a year ago

Could you show some examples of how you tested this?

user663031 Over a year ago

If the index is less than inputArray.length / 2, then by definition it will also be less than the ceiling of that value, so the second check would seem to be unnecessary, unless I'm missing something.

xourscode Over a year ago

In this approach the second check is necessary due to the first if statement. The first step is to check whether the array length is odd or not. When the length is not odd the inputArray.length / 2 check applies. Otherwise (when the array length is odd) the Math.ceil check applies. Even if this approach isn't the best (nor a good) one, the task will be solved with the suggested techniques of codeacadamy (and that's what this excercise is for).

Collectives™ on Stack Overflow

Finding elements in first half of Javascript array

2 Answers 2

Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related