Uncaught Error: Cannot find module 'openpgp'

I'm learning javascript, and I tried to import some modules using npm in my js file. For some module, import using require() works fine, but I don't know why, for openpgp.js I got a Uncaught Error: Cannot find module 'openpgp'.

Here the setup of my app : app config

I run npm install openpgp inside my js file. In my js I import modules by typing var openpgp = require('openpgp');, Then I refreshed my browser and see my error : browser error

For information, when I using the node console, modules works fine !

I'm realy new in javascript, so may be I do something wrong. If someone have an idea it's would be helpful !

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