JSFiddle - React, Tailwind, and code Playground

JavaScript

(function() {

  String.prototype.trimLines = function(){
    return this.split("\n").map(line=>line.trim()).join("\n");
  }

  if ( true ) {
    const str = `строка 1
    строка 2
    строка 3`;

    console.log(str);
    console.log(str.trimLines());
  }

}())