function logValidatorForCustomPageRequested(component, name, callbackName) {
    console.log(component);
    console.log(name);
    console.log(callbackName);
}

function validate() {
    console.log(">>> Validating...");
    return true;
}

function Component() {
    component.loaded.connect(this, Component.prototype.loaded);
    if (!installer.addWizardPage(component, "SomeWidget", QInstaller.ReadyForInstallation)) {
        console.log(">>> SomeWidget not added");
    }
    installer.setValidatorForCustomPageRequested.connect(this, logValidatorForCustomPageRequested);
}

Component.prototype.loaded = function () {
    console.log(">>> Loaded: " + component.name);
    installer.setValidatorForCustomPage(component, "SomeWidget", validate);
}