Time complexity of includes() function in JavaScript

Question

I have an array that contains some hash values of certain strings, I don\'t want duplicate values in my array so I use if logic like this

if(!a         


        

Answer 1

as my list is not sorted so i have create a dictionary and put values into it after checking if value present in it or not . Here in this dictionary my value and key are same .

var   arrayOfHashMap = {};/*is a dictionary,arrayOfValue is a list*/
    if(arrayOfHashMap[hash_value] !=hash_value){
                               arrayOfValue.push(hash_value); 
                               arrayOfHashMap[hash_value]=hash_value;
                        }

in this case I search values in o(1) time and put them in arrayOfValue

Answer 2

Spec describes this function as linear search. Array.prototype.includes

1. Let O be ? ToObject(this value).

2. Let len be ? ToLength(? Get(O, "length")).

3. If len is 0, return false.
4. Let n be ? ToInteger(fromIndex). (If fromIndex is undefined, this step produces the value 0.)
5. If n ≥ 0, then Let k be n.
6. Else n < 0, Let k be len + n. If k < 0, let k be 0.
7. Repeat, while k < len ... Increase k by 1.

Which is quite a reasonable choice in general case (list is not sorted, list is not uniform, you do not maintain additional datastructures along with the list itself).