npm uninstall -g @angular/cli
npm cache verify
npm install -g @angular/cli@latest

然后在本地项目包中:

rm -rf node_modules dist 
npm install --save-dev @angular/cli@latest
npm i 
ng update @angular/cli 
ng update @angular/core
npm install --save-dev @angular-devkit/build-angular

低于误差 错误:JSON输入意外结束 JSON输入意外结束 以上步骤不能将angular更新到版本6

npm uninstall -g @angular/cli
npm cache verify
npm install -g @angular/cli@latest

然后在本地项目包中:

rm -rf node_modules dist 
npm install --save-dev @angular/cli@latest
npm i 
ng update @angular/cli 
ng update @angular/core
npm install --save-dev @angular-devkit/build-angular

低于误差 错误:JSON输入意外结束 JSON输入意外结束 以上步骤不能将angular更新到版本6

还有另一种方法可以避免全局安装以创建新应用程序。 就我而言，我使用的是Angular 9，但客户需要的是Angular 8。

# create an empty directories
mkdir angular-8-cli
mkdir my-angular-8-project

# init empty npm project
cd angular-8-cli
npm init -y

# install local angular 8 cli
npm i @angular/cli@8

# go to your angular 8 project
cd ../my-angular-8-project

# use previously installed angular 8 cli to create a new angular 8 project
../angular-8-cli/node_modules/.bin/ng new my-angular-8-project --directory=.

在版本中

NPM install——save-dev @angular/cli@latest

关闭命令提示符并再次打开 ng版本 如果你的PowerShell不识别ng命令，在你的PowerShell运行这个命令:

Set-ExecutionPolicy -scope currentuser -executionpolicy remotessigned

这就是我解决问题的方法。

复制并运行这些命令

ng --version
npm install --save-dev @angular/cli@latest
ng --version

NPM install——save-dev @angular-devkit/build-angular - did帮助ng更新了@angular/cli -> did创建了angular。Json和其他更新。

收集已安装的依赖项… 发现58个依赖项。

 ** Executing migrations for package '@angular/cli' **
            Updating karma configuration
            Updating configuration
            Removing old config file (.angular-cli.json)
            Writing config file (angular.json)
            Some configuration options have been changed, please make sure to update any  npm scripts which you may have modified. DELETE .angular-cli.json CREATE angular.json (4394 bytes) CREATE browserslist (429 bytes) UPDATE karma.conf.js (993 bytes) UPDATE public/tsconfig.spec.json (295 bytes) UPDATE package.json (2618 bytes) UPDATE tsconfig.json (437 bytes) UPDATE tslint.json (3135 bytes) UPDATE public/polyfills.ts (587 bytes) UPDATE public/tsconfig.app.json (199 bytes) npm WARN @angular/core@5.2.9 requires a peer of zone.js@^0.8.4 but none is installed. You must install peer dependencies yourself.