JavaScript字符串是不可变的吗？我需要JavaScript中的"字符串构建器"吗？

let name = "John";
let age = 25;
let message = `Hello, my name is ${name}, and I am ${age} years old.`;

let stringBuilder = new StringBuilder();
stringBuilder.append("Hello, ");
stringBuilder.append("my name is ");
stringBuilder.append("John");
stringBuilder.append(", and I am ");
stringBuilder.append(25);
stringBuilder.append(" years old.");
let message = stringBuilder.toString();