Change width proportions of two blocks with a slider

Question

I\'m trying to design a component in which you could change the width proportions of two blocks by moving a slider left and right:

codpen and demo:

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Answer 1

You can adjust your flexbox along with resize - the downside is that the slider its not very customizeable:

• add resize: horizontal to one of the flex items
• add flex: 1 to the other flex item (so that this flex item will adjust automatically in response to the changing width of the other flex item as it is resized)

See demo below:

.outer {
  display: flex;
  flex-direction: row;
}

.block {
  height: 100px;
  width: 50%; /* 50% would suffice*/
}

.block-1 {
  background-color: red;
  resize: horizontal; /* resize horizontal */
  overflow: hidden; /* resize works for overflow other than visible */
}

.block-2 {
  background-color: green;
  flex: 1; /* adjust automatically */
}

<div id="app">
  <div class="outer">
    <div class="block block-1">
      Block 1
    </div>
    <div class="block block-2">
      Block 2
    </div>
  </div>
</div>

---

So we'll use vanilla JS instead of the resize solution above:

• use a mousedown listener that registers a mousemove listener that updates the block-1 width (and reset the mouseup event)
• also consider min-width: 0 to override min-width: auto of the block-2 element

See demo below:

let block = document.querySelector(".block-1"),
  slider = document.querySelector(".slider");

slider.onmousedown = function dragMouseDown(e) {
  let dragX = e.clientX;
  document.onmousemove = function onMouseMove(e) {
    block.style.width = block.offsetWidth + e.clientX - dragX + "px";
    dragX = e.clientX;
  }
  // remove mouse-move listener on mouse-up
  document.onmouseup = () => document.onmousemove = document.onmouseup = null;
}

.outer {
  display: flex;
  flex-direction: row;
}

.block {
  height: 100px;
  width: 50%; /* 50% would suffice*/
}

.block-1 {
  background-color: red;
}

.block-2 {
  background-color: green;
  flex: 1; /* adjust automatically */
  min-width: 0; /* allow flexing beyond auto width */
  overflow: hidden; /* hide overflow on small width */
}

.slider {
  line-height: 100%;
  width: 10px;
  background-color: #dee2e6;
  border: none;
  cursor: col-resize;
  user-select: none; /* disable selection */
  text-align: center;
}

<div id="app">
  <div class="outer">
    <div class="block block-1">
      Block 1
    </div>
    <div class="slider">
      S<br>l<br>i<br>d<br>e<br>r
    </div>
    <div class="block block-2">
      Block 2
    </div>
  </div>
</div>

---

Solution

You can adapt the above into Vue easily without using any custom Vue plugins for this - the changes are:

• @mousedown listener on slider that triggers the slider

• use of refs to update the width of block-1

See demo below:

new Vue({
  el: '#app',
  data: {
    block1W: '50%'
  },
  methods: {
    drag: function(e) {
      let dragX = e.clientX;
      let block = this.$refs.block1;
      document.onmousemove = function onMouseMove(e) {
        block.style.width = block.offsetWidth + e.clientX - dragX + "px";
        dragX = e.clientX;
      }
      // remove mouse-move listener on mouse-up
      document.onmouseup = () => document.onmousemove = document.onmouseup = null;
    }
  }
});

.outer {
  display: flex;
  flex-direction: row;
}

.block {
  height: 100px;
  width: 50%; /* 50% would suffice*/
}

.block-1 {
  background-color: red;
}

.block-2 {
  background-color: green;
  flex: 1; /* adjust automatically */
  min-width: 0; /* allow flexing beyond auto width */
  overflow: hidden; /* hide overflow on small width */
}

.slider {
  line-height: 100%;
  width: 10px;
  background-color: #dee2e6;
  border: none;
  cursor: col-resize;
  user-select: none; /* disable selection */
  text-align: center;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
  <div class="outer">
    <div class="block block-1" ref="block1" :style="{'width': block1W}">
      Block 1
    </div>
    <div class="slider" @mousedown="drag">
      S<br>l<br>i<br>d<br>e<br>r
    </div>
    <div class="block block-2">
      Block 2
    </div>
  </div>
</div>