getting the last item in a javascript object
JavascriptObjectJavascript Problem Overview
If I have an object like:
{ 'a' : 'apple', 'b' : 'banana', 'c' : 'carrot' }
If I don't know in advance that the list goes up to 'c', other than looping through the object, is there a way to get the last item in the object (e.g. 'carrot'
)?
Javascript Solutions
Solution 1 - Javascript
Yes, there is a way using Object.keys(obj)
. It is explained in this page:
var fruitObject = { 'a' : 'apple', 'b' : 'banana', 'c' : 'carrot' };
Object.keys(fruitObject); // this returns all properties in an array ["a", "b", "c"]
If you want to get the value of the last object, you could do this:
fruitObject[Object.keys(fruitObject)[Object.keys(fruitObject).length - 1]] // "carrot"
Solution 2 - Javascript
No. Order is not guaranteed in JSON and most other key-value data structures, so therefore the last item could sometimes be carrot
and at other times be banana
and so on. If you need to rely on ordering, your best bet is to go with arrays. The power of key-value data structures lies in accessing values by their keys
, not in being able to get the nth
item of the object.
Solution 3 - Javascript
last = Object.keys(obj)[Object.keys(obj).length-1];
where obj is your object
Solution 4 - Javascript
The other answers overcomplicate it for me.
let animals = {
a: 'dog',
b: 'cat',
c: 'bird'
}
let lastKey = Object.keys(animals).pop()
let lastValue = animals[Object.keys(animals).pop()]
Solution 5 - Javascript
var myObj = {a: 1, b: 2, c: 3}, lastProperty;
for (lastProperty in myObj);
lastProperty;
//"c";
Solution 6 - Javascript
Solution using the destructuring assignment syntax of ES6:
var temp = { 'a' : 'apple', 'b' : 'banana', 'c' : 'carrot' };
var { [Object.keys(temp).pop()]: lastItem } = temp;
console.info(lastItem); //"carrot"
Solution 7 - Javascript
You can try this. This will store last item. Here need to convert obj into array. Then use array pop()
function that will return last item from converted array.
var obj = { 'a' : 'apple', 'b' : 'banana', 'c' : 'carrot' };
var last = Object.keys(obj).pop();
console.log(last);
console.log(obj[last]);
Solution 8 - Javascript
Use an array, not an object literal, if order matters.
const list = ['apple', 'banana', 'carrot'];
Or something like
const dict = {
'a' : ['apple', 'awesome'],
'b' : ['best friend']
};
Or even..
const dict = [{letter:'a', list:['apple', 'awesome']},
{letter:'b', list:['best friend']}];
The keys for dict
are not guaranteed at all to be in order.
Solution 9 - Javascript
As for the ordering of object properties in Javascript, I will just link to this answer:
https://stackoverflow.com/questions/280713/elements-order-for-in-loop-in-javascript/280861#280861
Specifically:
> All modern implementations of > ECMAScript iterate through object > properties in the order in which they > were defined
So every other answer here is correct, there is no official guaranteed order to object properties. However in practice there is (barring any bugs which naturally can screw up even set-in-stone officially specified behavior).
Furthermore, the de-facto enumeration order of object properties is likely to be codified in future EMCAScript specs.
Still, at this time I would not write code around this, mostly because there are no built-in tools to help deal with object property order. You could write your own, but in the end you'd always be looping over each property in an object to determine its position.
As such the answer to your question is No, there is no way besides looping through an object.
Solution 10 - Javascript
JSArray = { 'a' : 'apple', 'b' : 'banana', 'c' : 'carrot' };
document.write(Object.keys(JSArray)[Object.keys(JSArray).length-1]);// writes 'c'
document.write(JSArray[Object.keys(JSArray)[Object.keys(JSArray).length-1]]); // writes 'carrot'
Solution 11 - Javascript
You could also use the Object.values()
method:
Object.values(fruitObject)[Object.values(fruitObject).length - 1]; // "carrot"
Edit
To improve performance, you could create a variable:
const fruitValues = Object.values(fruitObject);
To give you:
fruitValues[fruitValues.length - 1];
Solution 12 - Javascript
const fruitObject = { 'a' : 'apple', 'b' : 'banana', 'c' : 'carrot' };
const lastValue = Object.values(fruitObject).slice(-1)[0];
It seems to be a short way.
https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Object/values https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Array/slice
Solution 13 - Javascript
[Map object in JavaScript][1] [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map . This is already about 3 years old now. This map data structure retains the order in which items are inserted. With this retrieving last item will actually result in latest item inserted in the Map
Solution 14 - Javascript
Let obj
be your object. Exec:
(_ => _[Object.keys(_).pop()])( obj )
Solution 15 - Javascript
if you mean get the last key alphabetically, you can (garanteed) :
var obj = { 'a' : 'apple', 'b' : 'banana', 'c' : 'carrot' };
var keys = Object.keys(obj);
keys.sort();
var lastkey = keys.pop() // c
var lastvalue = obj[lastkey] // 'carrot'