build.js

const child_process = require("child_process");
const fs = require("fs").promises;
const buildCommand = "npx tsc";

(async () => {
    const tsconfig = await fs.readFile("tsconfig.json", "utf-8").then(json => JSON.parse(json.replace(/\\"|"(?:\\"|[^"])*"|(\/\/.*|\/\*[\s\S]*?\*\/)/g, (m, g) => g ? "" : m)));
    const buildPath = tsconfig.compilerOptions.outDir;
    if (!buildPath)
        throw new Error("no build path");
    try {
        if (!await fs.stat("node_modules"))
            throw new Error();
        console.log(buildCommand);
        await exec(buildCommand, {});
        const _package = JSON.parse(await fs.readFile("package.json", "utf-8"));
        delete _package.devDependencies;
        await fs.writeFile(buildPath + "/package.json", JSON.stringify(_package));
    } catch (_) {
        console.log("npm i");
        await exec("npm i");
        console.log(buildCommand);
        await exec(buildCommand);
        const package = JSON.parse(await fs.readFile("package.json", "utf-8"));
        delete package.devDependencies;
        await fs.writeFile(buildPath + "/package.json", JSON.stringify(package));
    }
})().catch(e => {
    throw e;
});

/**
 * @param {string} command
 * @param {{[src: string]: string} | boolean} pipe
 * @param {{[src: string]: string} | boolean} backpipe
 * @returns {Promise<void>}
*/
function exec(
    command,

    pipe = {
        stdout: "stdout",
        stderr: "stderr"
    },

    backpipe = {
        stdin: "stdin"
    }
) {
    if (typeof pipe !== "object" && pipe)
        pipe = {
            stdout: "stdout",
            stderr: "stderr"
        };
    if (typeof backpipe !== "object" && backpipe)
        backpipe = {
            stdout: "stdout",
            stderr: "stderr"
        };
    return new Promise((res, rej) => {
        const cp = child_process.exec(command, (err) => {
            if (err)
                rej(err);
            else
                res();
        }).on("spawn", () => {
            for (const name of Object.keys(pipe)) {
                let pn = pipe[name];
                if (typeof pn !== "string")
                    pn = name;
                cp[name].pipe(process[pn]);
            }
            for (const name of Object.keys(backpipe)) {
                let pn = backpipe[name];
                if (typeof pn !== "string")
                    pn = name;
                process[pn].pipe(cp[name]);
            }
        }).on("close", () => {
            try {
                for (const name of Object.keys(pipe)) {
                    let pn = pipe[name];
                    if (typeof pn !== "string")
                        pn = name;
                    cp[name].unpipe(process[pn]);
                }
                for (const name of Object.keys(backpipe)) {
                    let pn = backpipe[name];
                    if (typeof pn !== "string")
                        pn = name;
                    process[pn].unpipe(cp[name]);
                }
            } catch (_) { }
        });
    });
}