merge two strings based on char value in js code example

Example 1: string concatenation js

var aString="";
aString.concat(value1, value2, ... value_n);

Example 2: merge two strings with alternate characters javascript

var m = (a, b) => a.length ? [a[0], ...m(b, a.slice(1))] : b;
var string1 = "SCE ESG!";
var string2 = "ERTMSAE";
var mix = m(string1, string2);

console.log(mix.join(''));