Vue implements mouse drag control width

Vue.js is a popular JavaScript framework. It is not only a framework, but also a very flexible and powerful library. The framework allows developers to implement front-end applications efficiently. In this article, we will introduce how to use Vue.js to implement mouse drag control of width.

Implementing mouse drag to control width is a common interaction in many web applications, such as dragging a border bar or slider to resize a container or resize an image. The most basic UI part of this interaction is a draggable element and a container as the target element. In Vue.js, we use directives and event handlers to implement drag and drop.

The first step is to define an instruction that triggers dragging in the Vue instance. The "v-draggable" directive needs to be bound to the draggable element. This directive is registered as a global or local component using the Vue custom directive API.

Vue.directive('draggable', {
bind(el, binding, vnode) {

  let xOffset = 0;
  let yOffset = 0;

  const handleMouseDown = (event) => {
      if (!event.target.classList.contains('drag-handle')) {
          return;
      }

      xOffset = event.clientX;
      yOffset = event.clientY;

      document.addEventListener('mousemove', handleMouseMove);
      document.addEventListener('mouseup', handleMouseUp);
  };

  const handleMouseMove = (event) => {
      const currentX = event.clientX;
      const currentY = event.clientY;

      const dx = currentX - xOffset;
      const dy = currentY - yOffset;

      const newWidth = el.offsetWidth + dx;

      vnode.context[binding.expression] = newWidth;
  };

  const handleMouseUp = () => {
      document.removeEventListener('mousemove', handleMouseMove);
      document.removeEventListener('mouseup', handleMouseUp);
  };

  el.querySelector('.drag-handle').addEventListener('mousedown', handleMouseDown);

}
});

In the directive , we define a mouse down event (mousedown). We bind the event to the binding element (el) of the directive. After the event fires, we record the mouse offset relative to the element so that we can calculate the element's new position while dragging. We then calculate the offset in the mousemove event, figure out the new width and bind it into the Vue instance.

Finally, we bind the mouse release event (mouseup) to the document object so that the mouse release event can still be detected after the user leaves the drag area, and the mouse move and mouse release events are cleared of listeners.

Next, we use the "v-draggable" directive to bind the drag element to the data property of the Vue component.

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Vue.component('resizable', {
template: `

<div class="resizable">
  <div class="wrapper">
    <div class="panel-a">
      <div v-draggable="width" class="drag-area">
        <div class="drag-handle"></div>
      </div>
    </div>
    <div class="panel-b" :style="{ width: width + 'px' }"></div>
  </div>
</div>

`,
data() {

return {
  width: 400,
};

},
});

In this example, we create a React component "Resizable". It consists of a draggable area and a container. We use the v-draggable directive to bind the drag element to a width value, and the element is added to a container of class "drag-area".

Finally, we render the component into the DOM.

new Vue({
el: '#app',
});

In this way we successfully use Vue.js to implement mouse drag and drop to control the width of the dragged element . Vue.js provides a lot of flexibility and extensibility, making developing this kind of interaction very easy.

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