Neptunium, Promethium, Manganese


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    pileup.js is an interactive in-browser track viewer. Try a demo!

    It is built from the ground up to take advantage of the modern JavaScript ecosystem, e.g. ES2015, static type analysis, React.js and Promises. Read more about the motivations behind pileup.js in our paper.

    pileup.js screenshot

    Showing a structural variant (large deletion): pileup.js showing a large deletion


    To use pileup.js in a project, install it via NPM:

    npm install --save pileup

    And then source either node_modules/pileup/dist/pileup.min.js or pileup.js.

    To create a pileup, use pileup.create(). You specify a container DOM element, an initial range and a list of tracks:

    var div = document.getElementById('your-id');
    var p = pileup.create(div, {
      range: {contig: 'chr17', start: 7512384, stop: 7512544},
      tracks: [
          viz: pileup.viz.genome(),
          isReference: true,
          data: pileup.formats.twoBit({
            url: ''
          name: 'Reference'
          viz: pileup.viz.pileup(),
          data: pileup.formats.bam({
            url: '/test-data/synth3.normal.17.7500000-7515000.bam',
            indexUrl: '/test-data/synth3.normal.17.7500000-7515000.bam.bai'
          cssClass: 'normal',
          name: 'Alignments'
        // ...

    Each track has a name, a data source and a visualization. See /examples/playground.js for a complete set of track types.

    To style the track viewer, use CSS! pileup.js uses flexbox for track layout. You can view this codepen for a simple demo of the skeleton. For example, to allocate 1/3 of the space to a variant track and 2/3 to a pileup track, you could use this CSS:

    .track.variants { flex: 1; }
    .track.pileup   { flex: 2; }

    To style multiple tracks of the same type, you can use the cssClass property.


    The pileup object returned by pileup.create has these methods:

    • setRange: Update the visible range in the pileup. This takes a GenomeRange object, e.g. {contig: "chr17", start: 123, stop: 456}. The coordinates are 1-based and the range is inclusive on both ends.
    • getRange: Returns the currently-visible range. This is a GenomeRange object (see description in setRange).
    • zoomIn: Zooms current range in by a factor of 2.
    • zoomOut: Zooms current range out by a factor of 2.
    • toSvg: Converts pileup object to SVG data URL.
    • destroy: Tears down the pileup and releases references to allow proper garbage collection.

    If you want to change the set of tracks in a pileup, tear it down and create a new one. The caches are stored on the individual source and visualization objects so, as long as you reuse these, the destroy / create cycle is relatively cheap and will not incur extra trips to the network.


    Basic Setup

    git clone
    cd pileup.js
    npm install
    npm run build

    To play with the demo, start an http-server:

    npm run http-server

    Then open http://localhost:8080/examples/index.html in your browser of choice.

    To view integration with GA4GH schemas, view http://localhost:8080/examples/ga4gh-example.html.


    Run the tests from the command line:

    npm run test

    Run the tests in a real browser:

    npm run http-server
    open http://localhost:8080/src/test/runner.html

    To continuously regenerate the combined pileup and test JS, run:

    npm run watch

    To run a single test from the command line, use:

    npm run test -- --grep=pileuputils

    To do the same in the web UI, pass in a ?grep= URL parameter.

    To typecheck the code, run

    npm run flow

    For best results, use one of the flowtype editor integrations.



    If you're looking for ideas, see


    To cut a new release:

    • Update version in both package.json and pileup.js. Commit this change.
    • Run scripts/
    • Run npm publish
    • Push to github and tag a release there. Add release notes.


    pileup.js is Apache v2 licensed.


    npm i pileup

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    • danvk
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