Get the last item in an array

Question

Here is my JavaScript code so far:

var linkElement = document.getElementById(\"BackButton\");
var loc_array = document.location.href.split(\'/\');
var newT =         


        

Answer 1

You could add a new property getter to the prototype of Array so that it is accessible through all instances of Array.

Getters allow you to access the return value of a function just as if it were the value of a property. The return value of the function of course is the last value of the array (this[this.length - 1]).

Finally you wrap it in a condition that checks whether the last-property is still undefined (not defined by another script that might rely on it).

if(typeof Array.prototype.last === 'undefined') {
    Object.defineProperty(Array.prototype, 'last', {
        get : function() {
            return this[this.length - 1];
        }
    });
}

// Now you can access it like
[1, 2, 3].last;            // => 3
// or
var test = [50, 1000];
alert(test.last);          // Says '1000'

Does not work in IE ≤ 8.

Answer 2

I generally use underscorejs, with it you can just do

if (_.last(loc_array) === 'index.html'){
  etc...
}

For me that is more semantic than loc_array.slice(-1)[0]

Answer 3

You can add a last() function to the Array prototype.

Array.prototype.last = function () {
    return this[this.length - 1];
};

Answer 4

Not implemented yet!

The new TC39 Array.prototype.lastItem proposal (stage 1) adds a getter that returns the last item in an array:

const myArray = [1, 2, 3]

console.log(myArray.lastItem)
//=> 3

The Array.prototype.item proposal (stage 3) adds a different API:

const myArray = [1, 2, 3]

console.log(myArray.item(-1))
//=> 3

Answer 5

Use Array.pop:

var lastItem = anArray.pop();

Important : This returns the last element and removes it from the array

Answer 6

A shorter version of what @chaiguy posted:

Array.prototype.last = function() {
    return this[this.length - 1];
}

Reading the -1 index returns undefined already.

EDIT:

These days the preference seems to be using modules and to avoid touching the prototype or using a global namespace.

export function last(array) {
    return array[array.length - 1];
}