I was having the same issue when tried with the syntax "ng new " and solved that simply by updating the existing node version from 5.x.x to 8.x.x. After successful updation of node, the syntax worked perfectly for me. Please update the existing version of node. As it is clearly mentioned in angular documentation that these commands require the node version >= 6.9.x. For reference please check https://angular.io/guide/quickstart. It clearly states "Verify that you are running at least node 6.9.x and npm 3.x.x by running node -v and npm -v in a terminal/console window. Older versions produce errors, but newer versions are fine".

将C:\Users\DELL\AppData\Roaming\npm添加到系统变量路径对我来说很有效。请找到相应的“npm”文件路径

另外，检查是否已经将angular-cli\bin路径添加到path变量中。

关闭CMD并再次以管理员权限打开或重新启动系统。

这个方法几乎适用于我，但我必须使用:%USERPROFILE%\AppData\Roaming\npm ． 在环境变量中…/ /系统变量的路径

然后当我执行CMD: "ng -v"时，我得到了angular cli的正确响应。

设置路径= % %路径;C: \ \ \ AppData \ \ npm漫游用户

您可以这样办理登机手续。我也有同样的问题。首先，在环境变量中检查用户PATH。它必须指向%USERPROFILE%\AppData\Roaming\npm\node_modules\@angular\cli\

使用node.js命令提示符代替命令提示符。在安装的程序菜单中运行node.js命令提示符。点击开始，搜索node.js命令提示符。运行它，然后输入ng -v回车。它会起作用的。如果有帮助，请告诉我。