error after command $npm start

[chprerna110]

node ./index.js

internal/modules/cjs/loader.js:584
throw err;
^

Error: Cannot find module 'wrtc'
at Function.Module._resolveFilename (internal/modules/cjs/loader.js:582:15)
at Function.Module._load (internal/modules/cjs/loader.js:508:25)
at Module.require (internal/modules/cjs/loader.js:637:17)
at require (internal/modules/cjs/helpers.js:22:18)
at Object. (C:\Users\astrea\blockchain\P2p.js:1:76)
at Module._compile (internal/modules/cjs/loader.js:701:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:712:10)
at Module.load (internal/modules/cjs/loader.js:600:32)
at tryModuleLoad (internal/modules/cjs/loader.js:539:12)
at Function.Module._load (internal/modules/cjs/loader.js:531:3)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! blockchain-cli@2.0.0 start: node ./index.js
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the blockchain-cli@2.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! C:\Users\extra\AppData\Roaming\npm-cache_logs\2019-03-28T05_00_46_463Z-debug.log

please help me out of this error as soon as possibel