reasons.js

// Loop over every module, which looks like
// {
//     id: 1, reasons: [{ moduleId: 3 }]
//     id: 2, reasons: [{ moduleId: 3 }]
//     id: 3, reasons: []
// }
// and invert it to
// {
//  3: { dependencies: [ 1, 2 ] }
// }
const fileDependencies = stats.modules.reduce( ( memo, modjule ) => {

    return modjule.reasons.reduce( ( memo, reason ) => {
        const existing = memo[ reason.moduleId ] || [];

        const newAssign = {};
        newAssign[ reason.moduleId ] = existing.concat( modjule.id );

        return Object.assign( {}, memo, newAssign );

    }, memo );

}, {} );

modules
    .flatMap(module =>
        module.reasons.map(reason => ({ from: module.id, to: reason.moduleId }))
    )
    .reduce((graph, edge) => {
        graph[edge.to] = (graph[edge.to] || []).concat(edge.from);
        return graph;
    }, {})