TypeError: Cannot call a class as a function - ES6 - Angular1.x - Webpack

Question

Working on an Angular 1.x app, using ES6, an Angular Linter, and Babel for transpiling. I am receiving this error: "TypeError: Cannot call a class as a function" in the console, though the html loads just fine.

TypeError: Cannot call a class as a function
at _classCallCheck (bundle.js:97664)
at Object.loginNotifyService (bundle.js:97670)
at Object.invoke (bundle.js:23052)
at Object.enforcedReturnValue [as $get] (bundle.js:22885)
at Object.invoke (bundle.js:23052)
at bundle.js:22844
at getService (bundle.js:22993)
at injectionArgs (bundle.js:23018)
at Object.invoke (bundle.js:23044)
at $controllerInit (bundle.js:29012) "<div ui-view="" class="ng-scope">"

Best I can tell, syntax is correct. My best guess is Babel transpiling to ES5, specifically this:

function _classCallCheck(instance, Constructor) {
    if (!(instance instanceof Constructor)) {
        throw new TypeError("Cannot call a class as a function");
    }
}

Here is the source JS:

    'use strict';

class loginNotifyService {
    constructor (notify) {
        this.loginNotifyService = notify;
    }

    info (message, config) {
        config = config || {};
        config.message = message;
        config.classes = 'alert alert-info ' + (config.classes || '');
        return this.loginNotifyService(config);
    }

    warn (message, config) {
        config = config || {};
        config.message = message;
        config.classes = 'alert alert-warning ' + (config.classes || '');
        return this.loginNotifyService(config);
    }

    error (message, config) {
        config = config || {};
        config.message = message;
        config.classes = 'alert alert-danger ' + (config.classes || '');
        return this.loginNotifyService(config);
    }

    success (message, config) {
        config = config || {};
        config.message = message;
        config.classes = 'alert alert-success ' + (config.classes || '');
        return this.loginNotifyService(config);
    }

    notify (config) {
        return this.loginNotifyService(config);
    }

    closeAll () {
        return this.loginNotifyService.closeAll();
    }
}

// loginNotifyService.$inject = ['notify'];
/* @ngInject */
export default loginNotifyService;

Here is the Controller that the loginNotifyService interacts with:

'use strict';

class loginController {
    constructor ($state, loginNotifyService, loginService) {
        this.$state = $state;
        this.loginNotifyService = loginNotifyService;
        this.loginService = loginService;

        this.loginInProgress = false;
    }

    login () {
        this.loginNotifyService.closeAll();
        this.loginInProgress = true;
        this.loginService.login(this.email, this.password).then(
            () => {
                this.loginInProgress = false;
                this.$state.go('dashboard');
            },
            (error) => {
                this.loginInProgress = false;
                this.showErrors(error);
            }
        );
    }

    showErrors (error) {
        this.errors = error;
        this.loginNotifyService.error(error);
    }
}

// loginController.$inject = ['$state', 'loginNotifyService', 'loginService'];
/* @ngInject */
export default loginController;

LMK if further clarification or info needed, and thank you for any advice.

How is it being used? Can you post the code that is trying to use this? — Intervalia, Nov 03 '17 at 22:53
@Intervalia I added the controller that interacts with the loginNotifyService above. Thanks for taking a look! — maxmiles, Nov 04 '17 at 03:32

maxmiles · Accepted Answer · 2017-11-09T03:32:36.067

I was able to resolve this issue by changing the factory to a service. It was initially set as a factory due to a linting rule that I had set from this linter:

https://github.com/Gillespie59/eslint-plugin-angular

Here is the specific rule:

https://github.com/Gillespie59/eslint-plugin-angular/blob/master/docs/rules/no-service-method.md
(I had to disable this specific rule in order to make change from factory to service)

The structure of the loginNotifyService code needs to be a service in order to work correctly (as it is written currently). I was able to get a clearer understanding of the difference between the two by reading this post:

AngularJS : Factory and Service?

EXAMPLE:

angular
.module('commonModule', [           
    uiRouter,
    cgNotify,
    ngAnimate, 
    ngMaterial,
    ngMessages, 
    ngSanitize,
    ngAria,
    'navRoute',
    'mdTheme',
])

// ALL OF THE SERVICES BELOW WERE PREVIOUSLY FACTORIES.
// CHANGING "loginNotifyService" TO A SERVICE INSTEAD,
// FIXED THE "TypeError: Cannot call a class a function" ERROR!

.service('authService', authService)
.value('loginConfigService', loginConfigService)
.service('loginNotifyService', loginNotifyService)
.service('loginService', loginService)
.service('resetPassService', resetPassService)
.component('login', loginComponent)
.component('resetPass', resetPassComponent);

Also, thank you @Rhoden for your response and insights!

why does this make a difference? aren't services just factories under the hood? — Michael Davidson, Dec 04 '17 at 16:20

Gabriel Rohden · Answer 2 · 2020-12-09T18:08:02.323

This seems to be an 'understanding' error, AngularJS will not instantiate a 'transpiled'(compiled) service class unless it 'see' that it is a es6 class (as shown by the invoke code below).

Compiled classes by babel aren't classes, but functions acting as classes, so babel creates some checks (this function here: _classCallCheck) to prevent a class to be called as function (as they only should be 'called' with new keyword).

AngularJS on the invoke function uses this code:

function isClass(func) {
  // Support: IE 9-11 only
  // IE 9-11 do not support classes and IE9 leaks with the code below.
  if (msie || typeof func !== 'function') {
    return false;
  }
  var result = func.$$ngIsClass;
  if (!isBoolean(result)) {
    result = func.$$ngIsClass = /^class\b/.test(stringifyFn(func));
  }
  return result;
}

Which fails to detect babel compiled classes. So, this validation also fails:

if (!isClass(fn)) {
    // http://jsperf.com/angularjs-invoke-apply-vs-switch
    // #5388
     return fn.apply(self, args);
} else {
    args.unshift(null);
    return new (Function.prototype.bind.apply(fn, args))();
}

And you get a "TypeError: Cannot call a class as a function" error.

Edit: i was giving a look again at that code and you probably can declare a class like this to make this work:

class Foo {
  $$ngIsClass = true;
  // or
  static get $$ngIsClass = true;
}

This will force isClass to return true, and it will be called with the new keyword. (if you could test and confirm that it works i would be grateful).

Heh, who would've guessed that hardcoded intimation of type could fall over so easily :) — toxaq, Jun 12 '18 at 21:45

TypeError: Cannot call a class as a function - ES6 - Angular1.x - Webpack

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