Deploying to heroku causes mixed content error

Specifically after I deploy I get this: Mixed Content: The page at 'https://whatever.herokuapp.com/' was loaded over HTTPS, but requested an insecure script 'http://localhost:46655/static/js/client.js'. This request has been blocked; the content must be served over HTTPS.

My package.json looks like this:

{
  "name": "my-razzle-app",
  "version": "0.1.0",
  "license": "MIT",
  "scripts": {
    "start": "razzle start",
    "build": "razzle build",
    "test": "razzle test --env=jsdom",
    "start:prod": "NODE_ENV=production node build/server.js",
    "heroku-postbuild": "npm run build"
  },
  "dependencies": {
    ...
  }
}

[meeoh]

I changed my package.json to this

    "scripts": {
        "dev": "razzle start",
        "build": "razzle build",
        "test": "razzle test --env=jsdom",
        "start": "NODE_ENV=production node build/server.js",
        "heroku-postbuild": "npm run build"
    },

[applgeekam]

For Laravel project, add it where ? please