worker.js

/* global initSqlJs */
/* eslint-env worker */
/* eslint no-restricted-globals: ["error"] */

"use strict";

var db;

function onModuleReady(SQL) {
    function createDb(data) {
        if (db != null) db.close();
        db = new SQL.Database(data);
        return db;
    }

    var buff; var data; var result;
    data = this["data"];
    var config = data["config"] ? data["config"] : {};
    switch (data && data["action"]) {
        case "open":
            buff = data["buffer"];
            createDb(buff && new Uint8Array(buff));
            return postMessage({
                id: data["id"],
                ready: true
            });
        case "exec":
            if (db === null) {
                createDb();
            }
            if (!data["sql"]) {
                throw new Error("exec: Missing query string");
            }
            return postMessage({
                id: data["id"],
                results: db.exec(data["sql"], data["params"], config)
            });
        case "each":
            if (db === null) {
                createDb();
            }
            var callback = function callback(row) {
                return postMessage({
                    id: data["id"],
                    row: row,
                    finished: false
                });
            };
            var done = function done() {
                return postMessage({
                    id: data["id"],
                    finished: true
                });
            };
            return db.each(data["sql"], data["params"], callback, done, config);
        case "export":
            buff = db["export"]();
            result = {
                id: data["id"],
                buffer: buff
            };
            try {
                return postMessage(result, [result]);
            } catch (error) {
                return postMessage(result);
            }
        case "close":
            if (db) {
                db.close();
            }
            return postMessage({
                id: data["id"]
            });
        default:
            throw new Error("Invalid action : " + (data && data["action"]));
    }
}

function onError(err) {
    return postMessage({
        id: this["data"]["id"],
        error: err["message"]
    });
}

if (typeof importScripts === "function") {
    db = null;
    var sqlModuleReady = initSqlJs();
    self.onmessage = function onmessage(event) {
        return sqlModuleReady
            .then(onModuleReady.bind(event))
            .catch(onError.bind(event));
    };
}