Исправления JS для случаев отсутствия разметки JS-компонентов

src/blocks/nouislider/nouislider.js

 document.addEventListener('DOMContentLoaded', function(){
 
-  var demoNoUiSlider = document.getElementById('demo-nouislider');
-  var demoNoUiSliderStartInput = document.getElementById('demo-nouislider-start');
-  var demoNoUiSliderEndInput = document.getElementById('demo-nouislider-end');
-  noUiSlider.create(demoNoUiSlider, {
-    start: [demoNoUiSliderStartInput.value, demoNoUiSliderEndInput.value],
-    connect: true,
-    step: 1,
-    range: {
-      'min': 0,
-      'max': 100
-    }
-  });
-  demoNoUiSlider.noUiSlider.on('update', function( values, handle ) {
-    var value = values[handle];
-    if ( handle ) {
-      demoNoUiSliderEndInput.value = Math.round(value);
-    } else {
-      demoNoUiSliderStartInput.value = Math.round(value);
-    }
-  });
-  demoNoUiSliderEndInput.addEventListener('change', function(){
-    demoNoUiSlider.noUiSlider.set([null, this.value]);
-  });
-  demoNoUiSliderStartInput.addEventListener('change', function(){
-    demoNoUiSlider.noUiSlider.set([this.value, null]);
-  });
+  if(document.getElementById('demo-nouislider')) {
+
+    var demoNoUiSlider = document.getElementById('demo-nouislider');
+    var demoNoUiSliderStartInput = document.getElementById('demo-nouislider-start');
+    var demoNoUiSliderEndInput = document.getElementById('demo-nouislider-end');
+    noUiSlider.create(demoNoUiSlider, {
+      start: [demoNoUiSliderStartInput.value, demoNoUiSliderEndInput.value],
+      connect: true,
+      step: 1,
+      range: {
+        'min': 0,
+        'max': 100
+      }
+    });
+    demoNoUiSlider.noUiSlider.on('update', function( values, handle ) {
+      var value = values[handle];
+      if ( handle ) {
+        demoNoUiSliderEndInput.value = Math.round(value);
+      } else {
+        demoNoUiSliderStartInput.value = Math.round(value);
+      }
+    });
+    demoNoUiSliderEndInput.addEventListener('change', function(){
+      demoNoUiSlider.noUiSlider.set([null, this.value]);
+    });
+    demoNoUiSliderStartInput.addEventListener('change', function(){
+      demoNoUiSlider.noUiSlider.set([this.value, null]);
+    });
+
+  }
 
 });

src/blocks/swipe/swipe.js

 document.addEventListener('DOMContentLoaded', function(){
 
-  window.mySwipe = new Swipe(document.getElementById('swipe-demo'), {
-    startSlide: 0,
-    speed: 400,
-    auto: 3000,
-    draggable: true,
-    continuous: true,
-    disableScroll: true,
-    stopPropagation: true,
-    callback: function(index, elem, dir) {},
-    transitionEnd: function(index, elem) {}
-  });
+  if(document.getElementById('swipe-demo')) {
 
-  // включить видимость блока (по умолчанию скрыт)
-  document.getElementById('swipe-demo').classList.add('swipe--enable');
+    window.mySwipe = new Swipe(document.getElementById('swipe-demo'), {
+      startSlide: 0,
+      speed: 400,
+      auto: 3000,
+      draggable: true,
+      continuous: true,
+      disableScroll: true,
+      stopPropagation: true,
+      callback: function(index, elem, dir) {},
+      transitionEnd: function(index, elem) {}
+    });
 
+    // включить видимость блока (по умолчанию скрыт)
+    document.getElementById('swipe-demo').classList.add('swipe--enable');
+
+  }
 });

src/blocks/to-top/to-top.js

 document.addEventListener('DOMContentLoaded', function(){
 
-  document.querySelector('#to-top').addEventListener('click', function(e) {
-    e.preventDefault();
-    var scroll = window.pageYOffset;
-    var targetTop = 0;
-    var scrollDiff = (scroll - targetTop) * -1;
-    animate({
-      duration: 500,
-      timing: function(timeFraction) {
-        return Math.pow(timeFraction, 4); // https://learn.javascript.ru/js-animation
-      },
-      draw: function(progress) {
-        var scrollNow = scroll + progress * scrollDiff;
-        window.scrollTo(0,scrollNow);
-      }
-    });
-  }, false);
+  if(document.getElementById('to-top')) {
+
+    document.getElementById('to-top').addEventListener('click', function(e) {
+      e.preventDefault();
+      var scroll = window.pageYOffset;
+      var targetTop = 0;
+      var scrollDiff = (scroll - targetTop) * -1;
+      animate({
+        duration: 500,
+        timing: function(timeFraction) {
+          return Math.pow(timeFraction, 4); // https://learn.javascript.ru/js-animation
+        },
+        draw: function(progress) {
+          var scrollNow = scroll + progress * scrollDiff;
+          window.scrollTo(0,scrollNow);
+        }
+      });
+    }, false);
 
-  window.addEventListener('scroll', visibilityToggle);
-  visibilityToggle();
+    window.addEventListener('scroll', visibilityToggle);
+    visibilityToggle();
 
-  function visibilityToggle() {
-    if(window.pageYOffset >= 500) {
-      document.querySelector('#to-top').classList.add('to-top--visible');
+    function visibilityToggle() {
+      if(window.pageYOffset >= 500) {
+        document.getElementById('to-top').classList.add('to-top--visible');
+      }
+      else {
+        document.getElementById('to-top').classList.remove('to-top--visible');
+      }
     }
-    else {
-      document.querySelector('#to-top').classList.remove('to-top--visible');
+
+    function animate(_ref) {
+      var timing = _ref.timing,
+          draw = _ref.draw,
+          duration = _ref.duration;
+      var start = performance.now();
+      requestAnimationFrame(function animate(time) {
+        var timeFraction = (time - start) / duration;
+        if (timeFraction > 1) timeFraction = 1;
+        var progress = timing(timeFraction);
+        draw(progress);
+        if (timeFraction < 1) {
+          requestAnimationFrame(animate);
+        }
+      });
     }
-  }
 
-  function animate(_ref) {
-    var timing = _ref.timing,
-        draw = _ref.draw,
-        duration = _ref.duration;
-    var start = performance.now();
-    requestAnimationFrame(function animate(time) {
-      var timeFraction = (time - start) / duration;
-      if (timeFraction > 1) timeFraction = 1;
-      var progress = timing(timeFraction);
-      draw(progress);
-      if (timeFraction < 1) {
-        requestAnimationFrame(animate);
-      }
-    });
   }
 
 });