Combat7

const containerSelector = '#menu_left';
const itemSelector = `${containerSelector} li`;
const className = 'active';

$(itemSelector).click(function(e) {
  e.stopPropagation();
  $(this).addClass(className);
});

// или

document.querySelectorAll(itemSelector).forEach(function(n) {
  n.addEventListener('click', this);
}, e => {
  e.stopPropagation();
  e.currentTarget.classList.add(className);
});

$(containerSelector).click(e => {
  $(e.target).closest(itemSelector).addClass(className);
});

// или

document.querySelector(containerSelector).addEventListener('click', e => {
  const li = e.target.closest(itemSelector);
  if (li) {
    li.classList.add(className);
  }
});

.container {
    position: relative;
    width: 100px;
    height: 100px;
}

.container img {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    margin: auto;
    max-width: 100%;
    max-height: 100%;
    width: auto;
    height: auto;
}

class Class2 {
  function funct1() {
    $data1 = new Class1();
  }
}

$data1 = new Class1();

class Class2 {
  function funct1($data1) {
    
  }
}
Class2::funct1($data1);

let text = 'test1 test2 test3 test4';
let newLastWord = 'word';

let words = text.split(' ');
words[words.length - 1] = newLastWord;

text = words.join(' '); // "test1 test2 test3 word"