concatenate after in JAVASCRIPT

byMR

June 8, 2022

I have an array of strings.

For e.g. column_list=["ab","bc","cd","asv_a","asv_f","asv_l","asv_x", "xy","yz"].

Now I have another array with only the"asv_" value(which can be repeated or unique).

For e.g. new_column = ["asv_b", "asv_f", "asv_s"].

Now I want to create a new array by concatenating the new_column array to column_list such that all the asv_ values be together in the middle and unique.

Expected outcome –

result = ["ab","bc","cd","asv_a","asv_f","asv_l","asv_x","asv_b", "asv_s", "xy","yz"]

>Solution :

First, create a Set of asv_* values in column_list for use in eliminating duplicates

const asvValues = new Set(column_list.filter(v => v.startsWith("asv_")));

Then filter out duplicates

const inserts = new_column.filter(v => !asvValues.has(v));

Now, find the index of the last asv_ entry

const lastAsv = column_list.lastIndexOf([...asvValues].pop());

Now use splice() to insert the filtered array into the position found

column_list.splice(lastAsv + 1, 0, ...inserts);

const column_list=["ab","bc","cd","asv_a","asv_f","asv_l","asv_x", "xy","yz"];
const new_column = ["asv_b", "asv_f", "asv_s"];

const asvValues = new Set(column_list.filter((v) => v.startsWith("asv_")));
const inserts = new_column.filter((v) => !asvValues.has(v));
const lastAsv = column_list.lastIndexOf([...asvValues].pop());
column_list.splice(lastAsv + 1, 0, ...inserts);

console.log(column_list);