use angular-cli to build the project, because cli itself does not provide hot updates. Refer to tutorial and follow the tutorial steps to report errors all the time. The errors are as follows

Schema validation failed with the following errors:
  Data path "["build"]" should NOT have additional properties(hmr).
Error: Schema validation failed with the following errors:
  Data path "["build"]" should NOT have additional properties(hmr).
    at MergeMapSubscriber._registry.compile.pipe.operators_1.concatMap.validatorResult [as project] (/Users/work/Desktop/qlouduiframe/new-ui/node_modules/@angular-devkit/core/src/workspace/workspace.js:215:42)

use version information as follows

Angular CLI: 7.1.3
Node: 10.13.0
Angular: 7.1.3
npm: 6.5.0

I don"t know if it"s because of the version. The previous project using angular-cli 6.x version is normal, but I don"t know why 7.x version doesn"t work