fake_webpack.js

const MODULE_BODIES = {

    // This is the body of the file foo/index.ts, wrapped in a function
    ["./foo/index.ts"]: function (module) {
        const file = __webpack_resolve__("./foo/file.ts")
        module.exports.Service = file.Service
    },
    
    // This is the body of the file foo/file.ts, wrapped in a function
    ["./foo/file.ts"]: function (module) {
        module.exports.Service = Service;

        function Service() {
            console.log("hello")
        }
    },

}

// Once a module has been executed, it's stored in this object
// and pulled from here for every future resolve
const MODULE_CACHE = {}

// webpack replaces "import" and "require()" with a call to this function
function __webpack_resolve__(moduleName) {
    
    // Get it out of the cache if we've already imported the module
    let module = MODULE_CACHE[module];
    
    // Otherwise,
    if (!module) {
        
        // Find the module's body
        const module_body = MODULE_BODIES[moduleName]
        
        // Execute it, passing it a "module" object
        const module_object = {}
        module = module_body(module_object)
        
        // Store the exported module for future resolves
        MODULE_CACHE[moduleName] = module;
    }

    return module;
}