React Split Pane

Split-Pane component built with React, can be split vertically or horizontally.

Check out the demo

   <SplitPane split="vertical" minSize="50" defaultSize="100">
       <div></div>
       <div></div>
   </SplitPane>

    <SplitPane split="vertical" minSize="50">
        <div></div>
        <SplitPane split="horizontal">
            <div></div>
            <div></div>
        </SplitPane>
    </SplitPane>

Persisting Positions

Each SplitPane accepts an onChange function prop. Used in conjunction with defaultSize and a persistence layer, you can ensure that your splitter choices survive a refresh of your app.

For example, if you are comfortable with the trade-offs of localStorage, you could do something like the following:

    <SplitPane split="vertical" minSize="50"
               defaultSize={ localStorage.getItem('splitPos') }
               onChange={ size => localStorage.setItem('splitPos', size) }>
        <div></div>
        <div></div>
    </SplitPane>

Disclaimer: localStorage has a variety of performance trade-offs. Browsers such as Firefox have now optimized localStorage use so that they will asynchronously initiate a read of all saved localStorage data for an origin once they know the page will load. If the data has not fully loaded by the time code accesses localStorage, the code will cause the page's main thread to block until the database load completes. When the main thread is blocked, no other JS code will run or layout will occur. In multiprocess browsers and for users with fast disk storage, this will be less of a problem. You are likely to get yelled at if you use localStorage.

A potentially better idea is to use something like https://github.com/mozilla/localForage although hooking it up will be slightly more involved. You are likely to be admired by all for judiciously avoiding use of localStorage.

Example styling

This gives a single pixel wide divider, but with a 'grabbable' surface of 11 pixels.

Thanks to background-clip: padding-box; for making transparent borders possible.

    .Resizer {
        background: #000;
        opacity: .2;
        z-index: 1;
        -moz-box-sizing: border-box;
        -webkit-box-sizing: border-box;
        box-sizing: border-box;
        -moz-background-clip: padding;
        -webkit-background-clip: padding;
        background-clip: padding-box;
    }

     .Resizer:hover {
        -webkit-transition: all 2s ease;
        transition: all 2s ease;
    }

     .Resizer.horizontal {
        height: 11px;
        margin: -5px 0;
        border-top: 5px solid rgba(255, 255, 255, 0);
        border-bottom: 5px solid rgba(255, 255, 255, 0);
        cursor: row-resize;
        width: 100%;
    }

    .Resizer.horizontal:hover {
        border-top: 5px solid rgba(0, 0, 0, 0.5);
        border-bottom: 5px solid rgba(0, 0, 0, 0.5);
    }

    .Resizer.vertical {
        width: 11px;
        margin: 0 -5px;
        border-left: 5px solid rgba(255, 255, 255, 0);
        border-right: 5px solid rgba(255, 255, 255, 0);
        cursor: col-resize;
        height: 100%;
    }

    .Resizer.vertical:hover {
        border-left: 5px solid rgba(0, 0, 0, 0.5);
        border-right: 5px solid rgba(0, 0, 0, 0.5);
    }