JavaScript Arguments Object returning unexpected output

Question

I have a function that is supposed to check whether or not arguments passed to the function are undefined, and if any one of them is, then return false. I'm using node.js.

The issue I'm having is that logging the arguments object to the console is returning an unexpected output.

Here is my arrow function:

var checkYargsExist = () => {
    //console.log(arguments);
    for (x in arguments) {  
        if (arguments[x] === undefined) {
            return false;
        }
    }   
}

Suppose: var alpha = "apple"; var beta = "banana";

If I call the function as so: checkYargsExist(alpha, beta), I expect console.log() to spit out [alpha, beta], and compare "apple" === undefined, "banana" === undefined but my terminal is spitting out something like this:

{ '0': {},
  '1': 
   { [Function: require]
     resolve: [Function: resolve],
     main: 
      Module {
        id: '.',
        exports: {},
        parent: null,
        filename: '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/app.js',
        loaded: false,
        children: [Object],
        paths: [Object] },
     extensions: { '.js': [Function], '.json': [Function], '.node': [Function] },
     cache: 
      { '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/app.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/lodash/lodash.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/yargs/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/yargs/yargs.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/lodash.assign/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/yargs/lib/command.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/yargs/lib/completion.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/yargs-parser/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/camelcase/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/yargs-parser/lib/tokenize-arg-string.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/yargs/lib/usage.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/cliui/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/string-width/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/strip-ansi/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/ansi-regex/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/code-point-at/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/is-fullwidth-code-point/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/number-is-nan/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/wrap-ansi/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/decamelize/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/window-size/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/yargs/lib/obj-filter.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/set-blocking/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/yargs/lib/validation.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/y18n/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/read-pkg-up/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/find-up/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/path-exists/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/pinkie-promise/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/read-pkg/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/load-json-file/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/graceful-fs/graceful-fs.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/graceful-fs/polyfills.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/graceful-fs/fs.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/graceful-fs/legacy-streams.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/strip-bom/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/is-utf8/is-utf8.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/parse-json/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/error-ex/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/is-arrayish/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/parse-json/vendor/parse.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/parse-json/vendor/unicode.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/pify/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/normalize-package-data/lib/normalize.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/normalize-package-data/lib/fixer.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/semver/semver.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/validate-npm-package-license/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/spdx-expression-parse/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/spdx-expression-parse/parser.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/spdx-correct/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/spdx-license-ids/spdx-license-ids.json': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/hosted-git-info/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/hosted-git-info/git-host-info.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/hosted-git-info/git-host.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/is-builtin-module/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/builtin-modules/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/normalize-package-data/lib/extract_description.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/normalize-package-data/lib/typos.json': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/normalize-package-data/lib/make_warning.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/normalize-package-data/lib/warning_messages.json': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/path-type/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/pkg-conf/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/object-assign/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/symbol/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/require-main-filename/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/notes.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/os-locale/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/lcid/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/invert-kv/index.js': [Object],
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules/lcid/lcid.json': [Object] } },
  '2': 
   Module {
     id: '.',
     exports: {},
     parent: null,
     filename: '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/app.js',
     loaded: false,
     children: [ [Object], [Object], [Object] ],
     paths: 
      [ '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/node_modules',
        '/Users/raigovind93/Dropbox/Localhost/Coding/Node/node_modules',
        '/Users/raigovind93/Dropbox/Localhost/Coding/node_modules',
        '/Users/raigovind93/Dropbox/Localhost/node_modules',
        '/Users/raigovind93/Dropbox/node_modules',
        '/Users/raigovind93/node_modules',
        '/Users/node_modules',
        '/node_modules' ] },
  '3': '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app/app.js',
  '4': '/Users/raigovind93/Dropbox/Localhost/Coding/Node/notes-node-app' }

What am I doing wrong? Thanks!

The return statement stops the execution of a function and returns a value from that function. this means that you cannot put any code below the return statement. — Kevin Kloet
– Kevin Kloet, Commented Dec 7, 2016 at 8:28
You haven't passed arguments in arrow function so you have declared global @GovindRai ? — Yogesh Patel
– Yogesh Patel, Commented Dec 7, 2016 at 8:34
@YogeshPatel — The code is missing the bit where the function is called, so you can't tell that. — Quentin
– Quentin, Commented Dec 7, 2016 at 8:37
@Quentin i am asking him. I have put question mark at the end of sentence sir. — Yogesh Patel
– Yogesh Patel, Commented Dec 7, 2016 at 8:42

Quentin · Accepted Answer · 2016-12-07 08:32:54Z

4

From MDN:

An arrow function expression has a shorter syntax compared to function expressions and does not bind its own this, arguments, super, or new.target.

You are examining the arguments of the scope the function was created in.

If you want to use the arguments of the function, then don't create it using an arrow function. Stick to a regular function declaration or function expression instead.

answered Dec 7, 2016 at 8:32

Quentin

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1 Comment

Govind Rai Over a year ago

Ah, I never knew that! Just following a course where the instructor is really pushing arrow functions.. definitely have look into pros/cons! Thanks!

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