ES6 via jspm errors in Firefox, Edge, Vivaldi, but works in Chrome, Opera

I'm using ES6 via jspm + SystemJS + traceur according to jspm tutorial.

Everything works fine in Chrome and Opera, however, console posts various errors in other browsers.

Firefox: SyntaxError: class is a reserved identifier, uncaught exception: SyntaxError: class is a reserved identifier

Edge: SCRIPT1002: Syntax error, Potentially unhandled rejection [2] Syntax error

Vivaldi: Unexpected token =>

SystemJS readme states that it runs even IE8+.

My jspm.config.js:

System.config({
  baseURL: "/",
  defaultJSExtensions: true,
  transpiler: "traceur",
  babelOptions: {
    "optional": [
      "runtime",
      "optimisation.modules.system"
    ]
  },
  paths: {
    "github:*": "jspm_packages/github/*",
    "npm:*": "jspm_packages/npm/*"
  },
  shim: {
    "packages": {
      "assets/js/lib/tabs": {
        "main": "tabby",
        "format": "global",
        "deps": "jquery",
        "exports": "$.tabby"
      },
      "assets/js/lib/select": {
        "main": "selectify",
        "format": "global",
        "deps": "jquery",
        "exports": "$.selectify"
      }
    }
  },

  map: {
    "babel": "npm:babel-core@5.8.25",
    "babel-runtime": "npm:babel-runtime@5.8.25",
    "core-js": "npm:core-js@1.2.1",
    "jquery": "github:components/jquery@2.1.4",
    "jquery-mask-plugin": "npm:jquery-mask-plugin@1.13.4",
    "jquery-validation": "github:jzaefferer/jquery-validation@1.14.0",
    "selectify": "assets/js/lib/select",
    "tabby": "assets/js/lib/tabs",
    "traceur": "github:jmcriffey/bower-traceur@0.0.91",
    "traceur-runtime": "github:jmcriffey/bower-traceur-runtime@0.0.91",
    "github:jspm/nodelibs-assert@0.1.0": {
      "assert": "npm:assert@1.3.0"
    },
    "github:jspm/nodelibs-process@0.1.2": {
      "process": "npm:process@0.11.2"
    },
    "github:jspm/nodelibs-util@0.1.0": {
      "util": "npm:util@0.10.3"
    },
    "github:jzaefferer/jquery-validation@1.14.0": {
      "jquery": "github:components/jquery@2.1.4"
    },
    "npm:assert@1.3.0": {
      "util": "npm:util@0.10.3"
    },
    "npm:babel-runtime@5.8.25": {
      "process": "github:jspm/nodelibs-process@0.1.2"
    },
    "npm:core-js@1.2.1": {
      "fs": "github:jspm/nodelibs-fs@0.1.2",
      "process": "github:jspm/nodelibs-process@0.1.2",
      "systemjs-json": "github:systemjs/plugin-json@0.1.0"
    },
    "npm:inherits@2.0.1": {
      "util": "github:jspm/nodelibs-util@0.1.0"
    },
    "npm:process@0.11.2": {
      "assert": "github:jspm/nodelibs-assert@0.1.0"
    },
    "npm:util@0.10.3": {
      "inherits": "npm:inherits@2.0.1",
      "process": "github:jspm/nodelibs-process@0.1.2"
    }
  }
});

And package.json:

{
  "name": "project_name",
  "version": "1.0.0",
  "description": "project_description",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "project_author",
  "license": "ISC",
  "devDependencies": {
    "glob": "^5.0.15",
    "gulp": "^3.9.0",
    "gulp-autoprefixer": "^3.0.2",
    "gulp-concat-css": "^2.2.0",
    "gulp-imagemin": "^2.3.0",
    "gulp-jspm": "^0.3.2",
    "gulp-less": "^3.0.3",
    "gulp-minify-css": "^1.2.1",
    "gulp-notify": "^2.2.0",
    "gulp-rename": "^1.2.2",
    "imagemin-pngquant": "^4.2.0",
    "jspm": "^0.16.11"
  },
  "jspm": {
    "configFile": "jspm.config.js",
    "dependencies": {
      "jquery": "github:components/jquery@^2.1.4",
      "jquery-mask-plugin": "npm:jquery-mask-plugin@^1.13.4",
      "jquery-validation": "github:jzaefferer/jquery-validation@^1.14.0"
    },
    "devDependencies": {
      "babel": "npm:babel-core@^5.8.24",
      "babel-runtime": "npm:babel-runtime@^5.8.24",
      "core-js": "npm:core-js@^1.1.4",
      "traceur": "github:jmcriffey/bower-traceur@0.0.91",
      "traceur-runtime": "github:jmcriffey/bower-traceur-runtime@0.0.91"
    }
  }
}

Desperate to solve this situation, as I understand, that there could be many reasons for it. Maybe someone run across similar issue with that setup.

Got it.

This was due to one of the plugins, which was provided in jspm.config.js shim. The plugin was using an Immediately-Invoked Arrow Function notation and word class without any export directive, and thus, shim plugin wasn't transpiled into ES5.

So instead of using ES6 classes in third-party libraries (shim plugins) it should be build with simple prototypal inheritance.

Cost me several hours to find out.