Error while deploying Angular App (NodeJS) to Heroku - node.js

Question

I currently develop an angular5 app, and need to deploy it to Heroku.
This app is served using NodeJS.
After logging into Heroku, I create new app by:
heroku create angular-vbnmc
and it was successful, now i could open https://angular-vbnmc.herokuapp.com/ without problems, but still the content is blank, see picture below:
Then i deploy my app with following commands
git push heroku newFeatureBranch:master
Note: I didn't push my master branch but instead i push newFeatureBranch to remote heroku's master branch
and I got following error
Counting objects: 219, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (208/208), done.
Writing objects: 100% (219/219), 122.63 KiB | 3.50 MiB/s, done.
Total 219 (delta 111), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Node.js app detected
remote:
remote: -----> Creating runtime environment
remote:
remote: NPM_CONFIG_LOGLEVEL=error
remote: NODE_VERBOSE=false
remote: NODE_ENV=production
remote: NODE_MODULES_CACHE=true
remote:
remote: -----> Installing binaries
remote: engines.node (package.json): 8.9.4
remote: engines.npm (package.json): 5.6.0
remote:
remote: Resolving node version 8.9.4...
remote: Downloading and installing node 8.9.4...
remote: npm 5.6.0 already installed with node
remote:
remote: -----> Restoring cache
remote: Skipping cache restore (not-found)
remote:
remote: -----> Building dependencies
remote: Prebuild detected (node_modules already exists)
remote: Rebuilding any native modules
remote: bootstrap#4.0.0 /tmp/build_61c2abaea4d9525f4aeb3f08e81769a2/node_modules/bootstrap
remote: Installing any new modules (package.json)
remote:
remote: > uws#0.14.5 install /tmp/build_61c2abaea4d9525f4aeb3f08e81769a2/node_modules/uws
remote: > node-gyp rebuild > build_log.txt 2>&1 || exit 0
remote:
remote:
remote: > node-sass#4.7.2 install /tmp/build_61c2abaea4d9525f4aeb3f08e81769a2/node_modules/node-sass
remote: > node scripts/install.js
remote:
remote: Downloading binary from https://github.com/sass/node-sass/releases/download/v4.7.2/linux-x64-57_binding.node
remote: Download complete
remote: Binary saved to /tmp/build_61c2abaea4d9525f4aeb3f08e81769a2/node_modules/node-sass/vendor/linux-x64-57/binding.node
remote: Caching binary to /tmp/npmcache.ShxWb/node-sass/4.7.2/linux-x64-57_binding.node
remote:
remote: > uglifyjs-webpack-plugin#0.4.6 postinstall /tmp/build_61c2abaea4d9525f4aeb3f08e81769a2/node_modules/webpack/node_modules/uglifyjs-webpack-plugin
remote: > node lib/post_install.js
remote:
remote:
remote: > node-sass#4.7.2 postinstall /tmp/build_61c2abaea4d9525f4aeb3f08e81769a2/node_modules/node-sass
remote: > node scripts/build.js
remote:
remote: Binary found at /tmp/build_61c2abaea4d9525f4aeb3f08e81769a2/node_modules/node-sass/vendor/linux-x64-57/binding.node
remote: Testing binary
remote: Binary is fine
remote:
remote: > angular-vbnmc#0.0.0 postinstall /tmp/build_61c2abaea4d9525f4aeb3f08e81769a2
remote: > ng build --prod
remote:
remote:
remote: An error occured during the build:
remote: Error: ENOENT: no such file or directory, open '/tmp/build_61c2abaea4d9525f4aeb3f08e81769a2/node_modules/bootstrap/dist/js/bootstrap.min.js'
remote: ENOENT: no such file or directory, open '/tmp/build_61c2abaea4d9525f4aeb3f08e81769a2/node_modules/bootstrap/dist/js/bootstrap.min.js'
remote: Error: ENOENT: no such file or directory, open '/tmp/build_61c2abaea4d9525f4aeb3f08e81769a2/node_modules/bootstrap/dist/js/bootstrap.min.js'
remote: npm ERR! code ELIFECYCLE
remote: npm ERR! errno 1
remote: npm ERR! angular-vbnmc#0.0.0 postinstall: `ng build --prod`
remote: npm ERR! Exit status 1
remote: npm ERR!
remote: npm ERR! Failed at the angular-vbnmc#0.0.0 postinstall script.
remote: npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
remote:
remote: npm ERR! A complete log of this run can be found in:
remote: npm ERR! /tmp/npmcache.ShxWb/_logs/2018-03-06T04_54_08_334Z-debug.log
remote:
remote: -----> Build failed
remote:
remote: We're sorry this build is failing! You can troubleshoot common issues here:
remote: https://devcenter.heroku.com/articles/troubleshooting-node-deploys
remote:
remote: Some possible problems:
remote:
remote: - node_modules checked into source control
remote: https://blog.heroku.com/node-habits-2016#9-only-git-the-important-bits
remote:
remote: Love,
remote: Heroku
remote:
remote: ! Push rejected, failed to compile Node.js app.
remote:
remote: ! Push failed
remote: Verifying deploy...
remote:
remote: ! Push rejected to angular-vbnmc.
remote:
To https://git.heroku.com/angular-vbnmc.git
! [remote rejected] 12-Deployment -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/angular-vbnmc.git'
For additional information, here is my package.json:
{
"name": "angular-vbnmc",
"version": "0.0.0",
"license": "MIT",
"scripts": {
"ng": "ng",
"start": "node server.js",
"build": "ng build --prod",
"test": "ng test",
"lint": "ng lint",
"e2e": "ng e2e",
"postinstall": "ng build --prod"
},
"private": true,
"dependencies": {
"#angular/animations": "^5.2.7",
"#angular/cli": "1.6.6",
"#angular/common": "^5.2.7",
"#angular/compiler": "^5.2.7",
"#angular/compiler-cli": "^5.2.7",
"#angular/core": "^5.2.7",
"#angular/forms": "^5.2.7",
"#angular/http": "^5.2.7",
"#angular/platform-browser": "^5.2.7",
"#angular/platform-browser-dynamic": "^5.2.7",
"#angular/router": "^5.2.7",
"bootstrap": "^4.0.0",
"core-js": "^2.4.1",
"express": "^4.16.2",
"jquery": "^3.3.1",
"popper.js": "^1.13.0",
"rxjs": "^5.5.6",
"typescript": "^2.6.2",
"zone.js": "^0.8.19"
},
"devDependencies": {
"#angular/language-service": "^5.2.7",
"#types/jasmine": "~2.8.3",
"#types/jasminewd2": "~2.0.2",
"#types/node": "^6.0.101",
"codelyzer": "^4.2.1",
"jasmine-core": "~2.8.0",
"jasmine-spec-reporter": "~4.2.1",
"karma": "~2.0.0",
"karma-chrome-launcher": "~2.2.0",
"karma-coverage-istanbul-reporter": "^1.2.1",
"karma-jasmine": "~1.1.0",
"karma-jasmine-html-reporter": "^0.2.2",
"protractor": "~5.1.2",
"ts-node": "~4.1.0",
"tslint": "5.8.0"
},
"engines": {
"node": "8.9.4",
"npm": "5.6.0"
}
}
Why is this happening? and how to fix this error?