Webpack 4 : ERROR in Entry module not found: Error: Can't resolve './src'

I was trying to run webpack-4 first time

webpack ./src/js/app.js ./dist/app.bundle.js

it shows warning / error :

WARNING in configuration
The 'mode' option has not been set, webpack will fallback to 'production' for this value. Set 'mode' option to 'development' or 'production' to enable defaults for each environment.
You can also set it to 'none' to disable any default behavior. Learn more: https://webpack.js.org/concepts/mode/

ERROR in multi ./src/js/app.js ./dist/app.bundle.js
Module not found: Error: Can't resolve './dist/app.bundle.js' in 'D:\wamp64\www\webpack-4'
 @ multi ./src/js/app.js ./dist/app.bundle.js

Then i tried to change the mode

webpack --mode development

it shows :

ERROR in Entry module not found: Error: Can't resolve './src'

Resolved

Spent a lot of time to find out the solution.

Solution: Add index.js file into src folder.

That's it!.. solved :)

During Research, I found some facts about webpack 4 :

webpack 4 doesn’t need a configuration file by default!

webpack 4 there is no need to define the entry point: it will take ./src/index.js as the default!

Met this problem when deploying on now.sh

Solution: Use Default Behavior

Move entry point to src/index.js.

This leverage webpack@4 default value for entry:

By default its value is ./src/index.js, but you can specify a different (or multiple entry points) by configuring the entry property in the webpack configuration.

Solution: Be Specific

As @Lokeh pointed out, if you don't want to change your JS file location you can always use path.resolve() in your webpack.config.js:

entry: path.resolve(__dirname, 'src') + '/path/to/your/file.js',