JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdn.jsdelivr.net/gh/eu81273/jsfiddle-console/console.js"></script>

JavaScript

const conv = {
  c: function(text, obj) {return text.replace(new RegExp(`[${obj.reduce((s, {r}) => s += r, "")}]`, "g"), e => {
    const t = e.codePointAt(0);
    if ((t >= 48 && t <= 57) || (t >= 65 && t <= 90) || (t >= 97 && t <= 122)) {
      return obj.reduce((s, {r, d}) => {
        if (new RegExp(`[${r}]`).test(e)) s = String.fromCodePoint(e.codePointAt(0) + d);
        return s;
      }, "")
    }
    return e;
  })},
  bold: function(text) {return this.c(text, [{r: "0-9", d: 120734}, {r: "A-Z", d: 120211}, {r: "a-z", d: 120205}])},
  italic: function(text) {return this.c(text, [{r: "A-Z", d: 120263}, {r: "a-z", d: 120257}])},
  boldItalic: function(text) {return this.c(text, [{r: "A-Z", d: 120315}, {r: "a-z", d: 120309}])},
  underLine: function(text) {return text.length > 0 ? [...text].join("\u0332") + "\u0332" :""},
  strikethrough: function(text) {return text.length > 0 ? [...text].join("\u0336") + "\u0336" :""},
};

var text = "Sample value 123\nSample value 456\nSample value 789";
console.log(text) // Original text
console.log(conv.bold(text)) // Bold type
console.log(conv.italic(text)) // Italic type
console.log(conv.boldItalic(text)) // Bold-italic type
console.log(conv.underLine(text)) // Underline
console.log(conv.strikethrough(text)) // Strikethrough