Third party libraries not initializing correctly

Question

I have a slider menu that I need to initialize after render to make a menu a slider, but it never initializes correctly.

return <div id='drawer' style={cfg.state.displayDrawer() ? 'display:block' : 'display:none'}
        config={(el, isInitialized) => {
            if(!isInitialized) {
                new Swiper('#menu', {
                    slidesPerView: 4,
                    centeredSlides: true,
                    paginationClickable: true,
                    spaceBetween: 30
                });
            }
        }}>
        <div id='menu' class='swiper-container'>
            <div class='swiper-wrapper'>
                {ctrl.items().map((item, idx) => {
                    return <div class='swiper-slide'>
                        {console.log(item.name())}
                        {item.name()}
                    </div>
                })}
            </div>
        </div>
        <div id='content'>
            {m.component(ctrl.content)}
        </div>
    </div>

It runs at the right time, but whatever is happening inside Mithril (I can only assume) does not allow this to initialize it correctly. If I run this bit of code below in the console, then the menu initializes perfectly fine.

new Swiper('#menu', {
     slidesPerView: 4,
     centeredSlides: true,
     paginationClickable: true,
     spaceBetween: 30
});

Answer 1

Without seeing your code in action, it's difficult to imagine what might be causing the problem. I tried replicating the first demo from the Swiper site using Mithril and couldn't get that to work in a way that felt right - getting the slider to initialise as part of Mithril's config and manually initialising it produced the same awkward results. This suggests to me that there aren't any fundamental issues with using Mithril & Swiper together (although I would introduce an onunload hook in the ctrl or the config to ensure the Swiper instance is destroyed at the right time). Can you produce a reduced test case that demonstrates the problem you're having?

m.mount( document.body, {
  controller : function(){
    this.autoInit   = false

    this.items      = [1,2,3,4,5,6,7,8,9,10]

    this.target     = undefined

    this.initSwiper = () =>
      this.swiper = new Swiper( this.target )

    this.onunload   = () => {
      if( this.swiper )
        this.swiper.destroy()
    }
  },

  view : ctrl => [
    m( '.swiper-container', {
      config : ( el, isInitialized ) => {
        ctrl.target = el

        if( ctrl.autoInit && !isInitialized )
          ctrl.initSwiper()
      }
    },
      m( '.swiper-wrapper',
        m( '.swiper-wrapper',
          ctrl.items.map( number =>
            m( '.swiper-slide',
              'Slide ' + number
            )
          )
        )
      )
    ),

    m( '.controls',
      m( 'label',
        m( 'input[type=checkbox]', {
          checked  : ctrl.autoInit,
          onchange : e => 
            ctrl.autoInit = e.target.checked
        } ),

        `Auto-initialise Swiper with Mithril's config`
      ),
      
      m( 'button', {
        onclick : () =>
          m.redraw.strategy( 'all' )
      }, 
        'Mithril reinit'
      ),

      m( 'button', {
        onclick : () =>
          ctrl.initSwiper()
      }, 
        'Initialise Swiper'
      )
    )
  ]
} )

.controls {
  display: flex;
  position: fixed;
  left: 0;
  top: 0;
  right: 0;
  width: 100%;
  z-index: 100;
}

.controls > * {
  padding: .5em;
}

body {
  background: #eee;
  font-family: Helvetica Neue, Helvetica, Arial, sans-serif;
  font-size: 14px;
  color:#000;
  margin: 0;
  padding: 0;
}

.swiper-container {
  width: 500px;
  height: 300px;
  margin: 20px auto;
}

.swiper-slide {
  text-align: center;
  font-size: 18px;


  /* Center slide text vertically */
  display: -webkit-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  -webkit-box-pack: center;
  -ms-flex-pack: center;
  -webkit-justify-content: center;
  justify-content: center;
  -webkit-box-align: center;
  -ms-flex-align: center;
  -webkit-align-items: center;
  align-items: center;
}



/**/
/**
 * Swiper 3.3.1
 * Most modern mobile touch slider and framework with hardware accelerated transitions
 * 
 * http://www.idangero.us/swiper/
 * 
 * Copyright 2016, Vladimir Kharlampidi
 * The iDangero.us
 * http://www.idangero.us/
 * 
 * Licensed under MIT
 * 
 * Released on: February 7, 2016
 */
.swiper-container {
  margin: 0 auto;
  position: relative;
  overflow: hidden;
  /* Fix of Webkit flickering */
  z-index: 1;
}
.swiper-container-no-flexbox .swiper-slide {
  float: left;
}
.swiper-container-vertical > .swiper-wrapper {
  -webkit-box-orient: vertical;
  -moz-box-orient: vertical;
  -ms-flex-direction: column;
  -webkit-flex-direction: column;
  flex-direction: column;
}
.swiper-wrapper {
  position: relative;
  width: 100%;
  height: 100%;
  z-index: 1;
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  -webkit-transition-property: -webkit-transform;
  -moz-transition-property: -moz-transform;
  -o-transition-property: -o-transform;
  -ms-transition-property: -ms-transform;
  transition-property: transform;
  -webkit-box-sizing: content-box;
  -moz-box-sizing: content-box;
  box-sizing: content-box;
}
.swiper-container-android .swiper-slide,
.swiper-wrapper {
  -webkit-transform: translate3d(0px, 0, 0);
  -moz-transform: translate3d(0px, 0, 0);
  -o-transform: translate(0px, 0px);
  -ms-transform: translate3d(0px, 0, 0);
  transform: translate3d(0px, 0, 0);
}
.swiper-container-multirow > .swiper-wrapper {
  -webkit-box-lines: multiple;
  -moz-box-lines: multiple;
  -ms-flex-wrap: wrap;
  -webkit-flex-wrap: wrap;
  flex-wrap: wrap;
}
.swiper-container-free-mode > .swiper-wrapper {
  -webkit-transition-timing-function: ease-out;
  -moz-transition-timing-function: ease-out;
  -ms-transition-timing-function: ease-out;
  -o-transition-timing-function: ease-out;
  transition-timing-function: ease-out;
  margin: 0 auto;
}
.swiper-slide {
  -webkit-flex-shrink: 0;
  -ms-flex: 0 0 auto;
  flex-shrink: 0;
  width: 100%;
  height: 100%;
  position: relative;
}
/* Auto Height */
.swiper-container-autoheight,
.swiper-container-autoheight .swiper-slide {
  height: auto;
}
.swiper-container-autoheight .swiper-wrapper {
  -webkit-box-align: start;
  -ms-flex-align: start;
  -webkit-align-items: flex-start;
  align-items: flex-start;
  -webkit-transition-property: -webkit-transform, height;
  -moz-transition-property: -moz-transform;
  -o-transition-property: -o-transform;
  -ms-transition-property: -ms-transform;
  transition-property: transform, height;
}
/* a11y */
.swiper-container .swiper-notification {
  position: absolute;
  left: 0;
  top: 0;
  pointer-events: none;
  opacity: 0;
  z-index: -1000;
}
/* IE10 Windows Phone 8 Fixes */
.swiper-wp8-horizontal {
  -ms-touch-action: pan-y;
  touch-action: pan-y;
}
.swiper-wp8-vertical {
  -ms-touch-action: pan-x;
  touch-action: pan-x;
}
/* Arrows */
.swiper-button-prev,
.swiper-button-next {
  position: absolute;
  top: 50%;
  width: 27px;
  height: 44px;
  margin-top: -22px;
  z-index: 10;
  cursor: pointer;
  -moz-background-size: 27px 44px;
  -webkit-background-size: 27px 44px;
  background-size: 27px 44px;
  background-position: center;
  background-repeat: no-repeat;
}
.swiper-button-prev.swiper-button-disabled,
.swiper-button-next.swiper-button-disabled {
  opacity: 0.35;
  cursor: auto;
  pointer-events: none;
}
.swiper-button-prev,
.swiper-container-rtl .swiper-button-next {
  background-image: url("data:image/svg+xml;charset=utf-8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20viewBox%3D'0%200%2027%2044'%3E%3Cpath%20d%3D'M0%2C22L22%2C0l2.1%2C2.1L4.2%2C22l19.9%2C19.9L22%2C44L0%2C22L0%2C22L0%2C22z'%20fill%3D'%23007aff'%2F%3E%3C%2Fsvg%3E");
  left: 10px;
  right: auto;
}
.swiper-button-prev.swiper-button-black,
.swiper-container-rtl .swiper-button-next.swiper-button-black {
  background-image: url("data:image/svg+xml;charset=utf-8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20viewBox%3D'0%200%2027%2044'%3E%3Cpath%20d%3D'M0%2C22L22%2C0l2.1%2C2.1L4.2%2C22l19.9%2C19.9L22%2C44L0%2C22L0%2C22L0%2C22z'%20fill%3D'%23000000'%2F%3E%3C%2Fsvg%3E");
}
.swiper-button-prev.swiper-button-white,
.swiper-container-rtl .swiper-button-next.swiper-button-white {
  background-image: url("data:image/svg+xml;charset=utf-8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20viewBox%3D'0%200%2027%2044'%3E%3Cpath%20d%3D'M0%2C22L22%2C0l2.1%2C2.1L4.2%2C22l19.9%2C19.9L22%2C44L0%2C22L0%2C22L0%2C22z'%20fill%3D'%23ffffff'%2F%3E%3C%2Fsvg%3E");
}
.swiper-button-next,
.swiper-container-rtl .swiper-button-prev {
  background-image: url("data:image/svg+xml;charset=utf-8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20viewBox%3D'0%200%2027%2044'%3E%3Cpath%20d%3D'M27%2C22L27%2C22L5%2C44l-2.1-2.1L22.8%2C22L2.9%2C2.1L5%2C0L27%2C22L27%2C22z'%20fill%3D'%23007aff'%2F%3E%3C%2Fsvg%3E");
  right: 10px;
  left: auto;
}
.swiper-button-next.swiper-button-black,
.swiper-container-rtl .swiper-button-prev.swiper-button-black {
  background-image: url("data:image/svg+xml;charset=utf-8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20viewBox%3D'0%200%2027%2044'%3E%3Cpath%20d%3D'M27%2C22L27%2C22L5%2C44l-2.1-2.1L22.8%2C22L2.9%2C2.1L5%2C0L27%2C22L27%2C22z'%20fill%3D'%23000000'%2F%3E%3C%2Fsvg%3E");
}
.swiper-button-next.swiper-button-white,
.swiper-container-rtl .swiper-button-prev.swiper-button-white {
  background-image: url("data:image/svg+xml;charset=utf-8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20viewBox%3D'0%200%2027%2044'%3E%3Cpath%20d%3D'M27%2C22L27%2C22L5%2C44l-2.1-2.1L22.8%2C22L2.9%2C2.1L5%2C0L27%2C22L27%2C22z'%20fill%3D'%23ffffff'%2F%3E%3C%2Fsvg%3E");
}
/* Pagination Styles */
.swiper-pagination {
  position: absolute;
  text-align: center;
  -webkit-transition: 300ms;
  -moz-transition: 300ms;
  -o-transition: 300ms;
  transition: 300ms;
  -webkit-transform: translate3d(0, 0, 0);
  -ms-transform: translate3d(0, 0, 0);
  -o-transform: translate3d(0, 0, 0);
  transform: translate3d(0, 0, 0);
  z-index: 10;
}
.swiper-pagination.swiper-pagination-hidden {
  opacity: 0;
}
/* Common Styles */
.swiper-pagination-fraction,
.swiper-pagination-custom,
.swiper-container-horizontal > .swiper-pagination-bullets {
  bottom: 10px;
  left: 0;
  width: 100%;
}
/* Bullets */
.swiper-pagination-bullet {
  width: 8px;
  height: 8px;
  display: inline-block;
  border-radius: 100%;
  background: #000;
  opacity: 0.2;
}
button.swiper-pagination-bullet {
  border: none;
  margin: 0;
  padding: 0;
  box-shadow: none;
  -moz-appearance: none;
  -ms-appearance: none;
  -webkit-appearance: none;
  appearance: none;
}
.swiper-pagination-clickable .swiper-pagination-bullet {
  cursor: pointer;
}
.swiper-pagination-white .swiper-pagination-bullet {
  background: #fff;
}
.swiper-pagination-bullet-active {
  opacity: 1;
  background: #007aff;
}
.swiper-pagination-white .swiper-pagination-bullet-active {
  background: #fff;
}
.swiper-pagination-black .swiper-pagination-bullet-active {
  background: #000;
}
.swiper-container-vertical > .swiper-pagination-bullets {
  right: 10px;
  top: 50%;
  -webkit-transform: translate3d(0px, -50%, 0);
  -moz-transform: translate3d(0px, -50%, 0);
  -o-transform: translate(0px, -50%);
  -ms-transform: translate3d(0px, -50%, 0);
  transform: translate3d(0px, -50%, 0);
}
.swiper-container-vertical > .swiper-pagination-bullets .swiper-pagination-bullet {
  margin: 5px 0;
  display: block;
}
.swiper-container-horizontal > .swiper-pagination-bullets .swiper-pagination-bullet {
  margin: 0 5px;
}
/* Progress */
.swiper-pagination-progress {
  background: rgba(0, 0, 0, 0.25);
  position: absolute;
}
.swiper-pagination-progress .swiper-pagination-progressbar {
  background: #007aff;
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  -webkit-transform: scale(0);
  -ms-transform: scale(0);
  -o-transform: scale(0);
  transform: scale(0);
  -webkit-transform-origin: left top;
  -moz-transform-origin: left top;
  -ms-transform-origin: left top;
  -o-transform-origin: left top;
  transform-origin: left top;
}
.swiper-container-rtl .swiper-pagination-progress .swiper-pagination-progressbar {
  -webkit-transform-origin: right top;
  -moz-transform-origin: right top;
  -ms-transform-origin: right top;
  -o-transform-origin: right top;
  transform-origin: right top;
}
.swiper-container-horizontal > .swiper-pagination-progress {
  width: 100%;
  height: 4px;
  left: 0;
  top: 0;
}
.swiper-container-vertical > .swiper-pagination-progress {
  width: 4px;
  height: 100%;
  left: 0;
  top: 0;
}
.swiper-pagination-progress.swiper-pagination-white {
  background: rgba(255, 255, 255, 0.5);
}
.swiper-pagination-progress.swiper-pagination-white .swiper-pagination-progressbar {
  background: #fff;
}
.swiper-pagination-progress.swiper-pagination-black .swiper-pagination-progressbar {
  background: #000;
}
/* 3D Container */
.swiper-container-3d {
  -webkit-perspective: 1200px;
  -moz-perspective: 1200px;
  -o-perspective: 1200px;
  perspective: 1200px;
}
.swiper-container-3d .swiper-wrapper,
.swiper-container-3d .swiper-slide,
.swiper-container-3d .swiper-slide-shadow-left,
.swiper-container-3d .swiper-slide-shadow-right,
.swiper-container-3d .swiper-slide-shadow-top,
.swiper-container-3d .swiper-slide-shadow-bottom,
.swiper-container-3d .swiper-cube-shadow {
  -webkit-transform-style: preserve-3d;
  -moz-transform-style: preserve-3d;
  -ms-transform-style: preserve-3d;
  transform-style: preserve-3d;
}
.swiper-container-3d .swiper-slide-shadow-left,
.swiper-container-3d .swiper-slide-shadow-right,
.swiper-container-3d .swiper-slide-shadow-top,
.swiper-container-3d .swiper-slide-shadow-bottom {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 10;
}
.swiper-container-3d .swiper-slide-shadow-left {
  background-image: -webkit-gradient(linear, left top, right top, from(rgba(0, 0, 0, 0.5)), to(rgba(0, 0, 0, 0)));
  /* Safari 4+, Chrome */
  background-image: -webkit-linear-gradient(right, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Chrome 10+, Safari 5.1+, iOS 5+ */
  background-image: -moz-linear-gradient(right, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Firefox 3.6-15 */
  background-image: -o-linear-gradient(right, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Opera 11.10-12.00 */
  background-image: linear-gradient(to left, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Firefox 16+, IE10, Opera 12.50+ */
}
.swiper-container-3d .swiper-slide-shadow-right {
  background-image: -webkit-gradient(linear, right top, left top, from(rgba(0, 0, 0, 0.5)), to(rgba(0, 0, 0, 0)));
  /* Safari 4+, Chrome */
  background-image: -webkit-linear-gradient(left, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Chrome 10+, Safari 5.1+, iOS 5+ */
  background-image: -moz-linear-gradient(left, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Firefox 3.6-15 */
  background-image: -o-linear-gradient(left, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Opera 11.10-12.00 */
  background-image: linear-gradient(to right, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Firefox 16+, IE10, Opera 12.50+ */
}
.swiper-container-3d .swiper-slide-shadow-top {
  background-image: -webkit-gradient(linear, left top, left bottom, from(rgba(0, 0, 0, 0.5)), to(rgba(0, 0, 0, 0)));
  /* Safari 4+, Chrome */
  background-image: -webkit-linear-gradient(bottom, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Chrome 10+, Safari 5.1+, iOS 5+ */
  background-image: -moz-linear-gradient(bottom, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Firefox 3.6-15 */
  background-image: -o-linear-gradient(bottom, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Opera 11.10-12.00 */
  background-image: linear-gradient(to top, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Firefox 16+, IE10, Opera 12.50+ */
}
.swiper-container-3d .swiper-slide-shadow-bottom {
  background-image: -webkit-gradient(linear, left bottom, left top, from(rgba(0, 0, 0, 0.5)), to(rgba(0, 0, 0, 0)));
  /* Safari 4+, Chrome */
  background-image: -webkit-linear-gradient(top, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Chrome 10+, Safari 5.1+, iOS 5+ */
  background-image: -moz-linear-gradient(top, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Firefox 3.6-15 */
  background-image: -o-linear-gradient(top, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Opera 11.10-12.00 */
  background-image: linear-gradient(to bottom, rgba(0, 0, 0, 0.5), rgba(0, 0, 0, 0));
  /* Firefox 16+, IE10, Opera 12.50+ */
}
/* Coverflow */
.swiper-container-coverflow .swiper-wrapper,
.swiper-container-flip .swiper-wrapper {
  /* Windows 8 IE 10 fix */
  -ms-perspective: 1200px;
}
/* Cube + Flip */
.swiper-container-cube,
.swiper-container-flip {
  overflow: visible;
}
.swiper-container-cube .swiper-slide,
.swiper-container-flip .swiper-slide {
  pointer-events: none;
  -webkit-backface-visibility: hidden;
  -moz-backface-visibility: hidden;
  -ms-backface-visibility: hidden;
  backface-visibility: hidden;
  z-index: 1;
}
.swiper-container-cube .swiper-slide .swiper-slide,
.swiper-container-flip .swiper-slide .swiper-slide {
  pointer-events: none;
}
.swiper-container-cube .swiper-slide-active,
.swiper-container-flip .swiper-slide-active,
.swiper-container-cube .swiper-slide-active .swiper-slide-active,
.swiper-container-flip .swiper-slide-active .swiper-slide-active {
  pointer-events: auto;
}
.swiper-container-cube .swiper-slide-shadow-top,
.swiper-container-flip .swiper-slide-shadow-top,
.swiper-container-cube .swiper-slide-shadow-bottom,
.swiper-container-flip .swiper-slide-shadow-bottom,
.swiper-container-cube .swiper-slide-shadow-left,
.swiper-container-flip .swiper-slide-shadow-left,
.swiper-container-cube .swiper-slide-shadow-right,
.swiper-container-flip .swiper-slide-shadow-right {
  z-index: 0;
  -webkit-backface-visibility: hidden;
  -moz-backface-visibility: hidden;
  -ms-backface-visibility: hidden;
  backface-visibility: hidden;
}
/* Cube */
.swiper-container-cube .swiper-slide {
  visibility: hidden;
  -webkit-transform-origin: 0 0;
  -moz-transform-origin: 0 0;
  -ms-transform-origin: 0 0;
  transform-origin: 0 0;
  width: 100%;
  height: 100%;
}
.swiper-container-cube.swiper-container-rtl .swiper-slide {
  -webkit-transform-origin: 100% 0;
  -moz-transform-origin: 100% 0;
  -ms-transform-origin: 100% 0;
  transform-origin: 100% 0;
}
.swiper-container-cube .swiper-slide-active,
.swiper-container-cube .swiper-slide-next,
.swiper-container-cube .swiper-slide-prev,
.swiper-container-cube .swiper-slide-next + .swiper-slide {
  pointer-events: auto;
  visibility: visible;
}
.swiper-container-cube .swiper-cube-shadow {
  position: absolute;
  left: 0;
  bottom: 0px;
  width: 100%;
  height: 100%;
  background: #000;
  opacity: 0.6;
  -webkit-filter: blur(50px);
  filter: blur(50px);
  z-index: 0;
}
/* Fade */
.swiper-container-fade.swiper-container-free-mode .swiper-slide {
  -webkit-transition-timing-function: ease-out;
  -moz-transition-timing-function: ease-out;
  -ms-transition-timing-function: ease-out;
  -o-transition-timing-function: ease-out;
  transition-timing-function: ease-out;
}
.swiper-container-fade .swiper-slide {
  pointer-events: none;
  -webkit-transition-property: opacity;
  -moz-transition-property: opacity;
  -o-transition-property: opacity;
  transition-property: opacity;
}
.swiper-container-fade .swiper-slide .swiper-slide {
  pointer-events: none;
}
.swiper-container-fade .swiper-slide-active,
.swiper-container-fade .swiper-slide-active .swiper-slide-active {
  pointer-events: auto;
}
/* Scrollbar */
.swiper-scrollbar {
  border-radius: 10px;
  position: relative;
  -ms-touch-action: none;
  background: rgba(0, 0, 0, 0.1);
}
.swiper-container-horizontal > .swiper-scrollbar {
  position: absolute;
  left: 1%;
  bottom: 3px;
  z-index: 50;
  height: 5px;
  width: 98%;
}
.swiper-container-vertical > .swiper-scrollbar {
  position: absolute;
  right: 3px;
  top: 1%;
  z-index: 50;
  width: 5px;
  height: 98%;
}
.swiper-scrollbar-drag {
  height: 100%;
  width: 100%;
  position: relative;
  background: rgba(0, 0, 0, 0.5);
  border-radius: 10px;
  left: 0;
  top: 0;
}
.swiper-scrollbar-cursor-drag {
  cursor: move;
}
/* Preloader */
.swiper-lazy-preloader {
  width: 42px;
  height: 42px;
  position: absolute;
  left: 50%;
  top: 50%;
  margin-left: -21px;
  margin-top: -21px;
  z-index: 10;
  -webkit-transform-origin: 50%;
  -moz-transform-origin: 50%;
  transform-origin: 50%;
  -webkit-animation: swiper-preloader-spin 1s steps(12, end) infinite;
  -moz-animation: swiper-preloader-spin 1s steps(12, end) infinite;
  animation: swiper-preloader-spin 1s steps(12, end) infinite;
}
.swiper-lazy-preloader:after {
  display: block;
  content: "";
  width: 100%;
  height: 100%;
  background-image: url("data:image/svg+xml;charset=utf-8,%3Csvg%20viewBox%3D'0%200%20120%20120'%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20xmlns%3Axlink%3D'http%3A%2F%2Fwww.w3.org%2F1999%2Fxlink'%3E%3Cdefs%3E%3Cline%20id%3D'l'%20x1%3D'60'%20x2%3D'60'%20y1%3D'7'%20y2%3D'27'%20stroke%3D'%236c6c6c'%20stroke-width%3D'11'%20stroke-linecap%3D'round'%2F%3E%3C%2Fdefs%3E%3Cg%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%20transform%3D'rotate(30%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%20transform%3D'rotate(60%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%20transform%3D'rotate(90%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%20transform%3D'rotate(120%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%20transform%3D'rotate(150%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.37'%20transform%3D'rotate(180%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.46'%20transform%3D'rotate(210%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.56'%20transform%3D'rotate(240%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.66'%20transform%3D'rotate(270%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.75'%20transform%3D'rotate(300%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.85'%20transform%3D'rotate(330%2060%2C60)'%2F%3E%3C%2Fg%3E%3C%2Fsvg%3E");
  background-position: 50%;
  -webkit-background-size: 100%;
  background-size: 100%;
  background-repeat: no-repeat;
}
.swiper-lazy-preloader-white:after {
  background-image: url("data:image/svg+xml;charset=utf-8,%3Csvg%20viewBox%3D'0%200%20120%20120'%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20xmlns%3Axlink%3D'http%3A%2F%2Fwww.w3.org%2F1999%2Fxlink'%3E%3Cdefs%3E%3Cline%20id%3D'l'%20x1%3D'60'%20x2%3D'60'%20y1%3D'7'%20y2%3D'27'%20stroke%3D'%23fff'%20stroke-width%3D'11'%20stroke-linecap%3D'round'%2F%3E%3C%2Fdefs%3E%3Cg%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%20transform%3D'rotate(30%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%20transform%3D'rotate(60%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%20transform%3D'rotate(90%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%20transform%3D'rotate(120%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.27'%20transform%3D'rotate(150%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.37'%20transform%3D'rotate(180%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.46'%20transform%3D'rotate(210%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.56'%20transform%3D'rotate(240%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.66'%20transform%3D'rotate(270%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.75'%20transform%3D'rotate(300%2060%2C60)'%2F%3E%3Cuse%20xlink%3Ahref%3D'%23l'%20opacity%3D'.85'%20transform%3D'rotate(330%2060%2C60)'%2F%3E%3C%2Fg%3E%3C%2Fsvg%3E");
}
@-webkit-keyframes swiper-preloader-spin {
  100% {
    -webkit-transform: rotate(360deg);
  }
}
@keyframes swiper-preloader-spin {
  100% {
    transform: rotate(360deg);
  }
}

<link href="http://cdnjs.cloudflare.com/ajax/libs/Swiper/3.3.1/css/swiper.css" rel="stylesheet"/>
<script src="http://cdnjs.cloudflare.com/ajax/libs/Swiper/3.3.1/js/swiper.js"></script>
<script src="http://cdn.rawgit.com/lhorie/mithril.js/next/mithril.js"></script>

Answer 2

I believe (am guessing) the #menu element hasn't been created by the time the first config runs, a simple way to test this hypothesis could be to add a console.log('menu exists: ' + !!document.getElementById('menu')) as the first line of the config function.

Personally, I've tackled equivalent situations by creating a prop to track the element I'm trying to target, and then calling the config function again with a setTimeout/requestAnimationFrame if the element isn't ready yet. (I've also infinite looped myself as well, so maybe be a tad cautious :-p )

I prefer to use a prop rather than accessing the dom directly.

I also like using the ctx.swiper = new Swiper... style to facilitate adding an onunload cleanup function.

Fiddle example (ish, I had to hack together fake content and props, and had to convert the msx syntax) here: https://jsfiddle.net/98p3wptf/5/

(Afaict it's working because I can swipe the something and something2? (I don't know anything about Swiper.))