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

Performance

Today 2020.05.16 I perform tests of chosen solutions on Chrome v81.0, Safari v13.1 and Firefox v76.0 on MacOs High Sierra v10.13.6

Conclusions

• arr[arr.length-1] (D) is recommended as fastest cross-browser solution
• mutable solution arr.pop() (A) and immutable _.last(arr) (L) are fast
• solutions I, J are slow for long strings
• solutions H, K (jQuery) are slowest on all browsers

Details

I test two cases for solutions:

• mutable: A, B, C,

• immutable: D, E, F, G, H, I, J (my),

• immutable from external libraries: K, L, M,

for two cases

• short string - 10 characters - you can run test HERE
• long string - 1M characters - you can run test HERE

function A(arr) {
  return arr.pop();
}

function B(arr) {  
  return arr.splice(-1,1);
}

function C(arr) {  
  return arr.reverse()[0]
}

function D(arr) {
  return arr[arr.length - 1];
}

function E(arr) {
  return arr.slice(-1)[0] ;
}

function F(arr) {
  let [last] = arr.slice(-1);
  return last;
}

function G(arr) {
  return arr.slice(-1).pop();
}

function H(arr) {
  return [...arr].pop();
}

function I(arr) {  
  return arr.reduceRight(a => a);
}

function J(arr) {  
  return arr.find((e,i,a)=> a.length==i+1);
}

function K(arr) {  
  return $(arr).get(-1);
}

function L(arr) {  
  return _.last(arr);
}

function M(arr) {  
  return _.nth(arr, -1);
}






// ----------
// TEST
// ----------

let loc_array=["domain","a","b","c","d","e","f","g","h","file"];

log = (f)=> console.log(`${f.name}: ${f([...loc_array])}`);

[A,B,C,D,E,F,G,H,I,J,K,L,M].forEach(f=> log(f));

Example results for Chrome for short string