I'm trying to return the last element in an array or, if the array is empty it should return null. What am I doing wrong / what is the best way to do this?
Here's my code:
function lastElement(x, y, z) { if (lastElement.length < 1 || lastElement === undefined) { return null; } else { return(lastElement[lastElement.length - 1]); } } You need to use a local variable which has a different name as the function, preferably a paramter and check if an array is handed over which has a length.
Then return the last item or null;
function getLastElement(array) { return Array.isArray(array) && array.length ? array[array.length - 1] : null; } console.log(getLastElement()); // null console.log(getLastElement([])); // null console.log(getLastElement([1])); // 1 console.log(getLastElement([1, 2])); // 2With the at method, the optional chaining and nullish coalescing operators, you can do:
const lastElement = array => array?.at?.(-1) ?? null; // demo console.log(lastElement([1,2,3])); // 3 console.log(lastElement([])); // null console.log(lastElement(42)); // null console.log(lastElement()); // null
lastElement is the name of your function.
You need to use array for this, Maybe this way:
function lastElement(array) { if (array.length < 1 || array === undefined) { return null; } else { return(array[array.length - 1]); } }You do not need a function for this you can just use the .length property. Also if you don't care if its undefined (when the array is empty) you can remove the. || null
let some_array = [1,2,3,4] let last_element = some_array[some_array.length-1] || null console.log(last_element)If you where do really need this in a function
let some_array = [1,2,3,4] function get_last(array){ //if the array is empty return null return array[array.length-1] || null } console.log(get_last(some_array)) console.log(get_last([]))No need for any custom function. You can use any of the following process.
let arrItems = ['a', 'b', 'c', 'd']; console.log('using array length'); let lastItem = arrItems[arrItems.length - 1]; console.log(lastItem); console.log('using slice method'); let lastItem1 = arrItems.slice(-1)[0]; console.log(lastItem1); console.log('using pop method'); let lastItem2 = arrItems.pop(); console.log(lastItem2); //Output: // using array length // d // using slice method // d // using pop method // d
pop() mutates the original array, therefore it is not a getter.
slice creates an intermediate array, which is overkill for just retrieving a value.
return lastElement.slice(-1)suffice? --- Also why are you referencinglastElement? That's the function name.x,y, andzare never used.