Replacing an array with an index values of the String

simple.js

// es6 syntax

var arr = ["a","b","c"];
var str = "Hello {1} is a friend of {2} and {3}";

var result_es6 = arr.reduce((str_data, replacement, idx) => {
  return str_data.replace(`{${idx + 1}}`, replacement)
}, str);

console.log(result_es6); // "Hello a is a friend of b and c"

// es5 syntax

var result_es5 = arr.reduce(function (str_data, replacement, idx) {
  return str_data.replace("{" + (idx + 1) + "}", replacement);
}, str);

console.log(result_es5); // "Hello a is a friend of b and c"