The Angular Compiler requires TypeScript >=2.7.2 and <2.8.0 but 2.8.3 was found instead

You should do npm install typescript@'>=2.7.2 <2.8.0'. This will install the correct typescript your project needs. Make sure you run this inside your Angular project.

On Windows, you should use double quotes instead of single quotes, like so:

npm install typescript@">=2.7.2 <2.8.0"

Otherwise, you'll get The system cannot find the file specified..

In your project folder run again npm install [email protected] as stated from here:

Want to upgrade project from Angular v5 to Angular v6

Then it should work.

I did next steps:

• removed package-lock.json;
• npm install -g --save [email protected];
• npm uninstall -g --save [email protected];
• in package.json, section "devDependencies" updated string with typescript as "typescript": "~2.7.2".

After all above run in project's terminal ng serve --open (I've been using IDEA 2018.1).