test25.js

// write a js function to extract unique characters from a string

// ======================================== < basic method > =============================================================
var pushUniqueChar = (str) =>    str.split("").filter((item,index,arr)  => arr.slice(index+1).indexOf(item) === -1);

// ================================================ < second method (using available function new Set) > ========================================================

var pushUniqueChar = (str) => [...(new Set(str.split("")))];
console.log(pushUniqueChar("aaaaaaaaaaaaabbbbbbbbcccccccc"));