Почему код работает на одной странице, но не работает на другой?

function InfoChange(btnEvent, inputsToChange, classToBlock, buttonTextChange) { 
  this.btnEvent = document.querySelector(btnEvent); 
  this.inputsToChange = document.querySelectorAll(inputsToChange); 
  this.classToBlock = classToBlock; 
  this.buttonTextChange = buttonTextChange; 
  this.currentBtnText = this.btnEvent.textContent; 
  var _this = this; 
 
  this.ready = this.btnEvent && this.inputsToChange; 
 
  if(!this.ready) { 
    return; 
  }; 
 
  var buttonAttr = function() { 
  	_this.btnEvent.setAttribute('data-status', 'unactive'); 
  }; 
  buttonAttr(); 
   
  this.btnEvent.addEventListener('click', function() { 
    var btnAttribute =  _this.btnEvent.getAttribute('data-status'); 
 
    if (btnAttribute == 'unactive') { 
      _this.btnEvent.setAttribute('data-status', 'active'); 
      _this.btnEvent.textContent = _this.buttonTextChange; 
    } else { 
      _this.btnEvent.setAttribute('data-status', 'unactive'); 
      _this.btnEvent.textContent = _this.currentBtnText; 
    }; 
     
    for(var i = 0; i < _this.inputsToChange.length; i++) { 
       
      _this.inputsToChange[i].addEventListener('change', function(event) { 
        var currentItem = event.target; 
        var currentValue = event.target.value; 
        currentItem.setAttribute('value', currentValue); 
 
      }); 
       
      if(_this.inputsToChange[i].classList.contains(classToBlock)) { 
      	_this.inputsToChange[i].classList.remove(classToBlock); 
      	_this.inputsToChange[i].removeAttribute('disabled'); 
      } else { 
      	_this.inputsToChange[i].classList.add(classToBlock); 
      	_this.inputsToChange[i].setAttribute('disabled', ''); 
      }; 
    }; 
 
  }); 
}; 
 
 
var changeInputs = new InfoChange('.button--profile-change', '.textinput-container__input--change', 'textinput-container__input--change-unactive', 'save'); 
var changePass = new InfoChange('.button--profile--change-pass', '.textinput-container__input--change-pass', 'textinput-container__input--change-unactive', 'save'); 
var changePass = new InfoChange('.button--profile--from-to', '.textinput-container__input--from-to', 'textinput-container__input--change-unactive', 'update'); 
var changeCV = new InfoChange('button', 'input', 'un', 'save');

.un { 
  border: none; 
  background-color: red; 
}

<input type="text"> 
<button>Button</button>