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.