Define attribute of UMI

meaning ：

Used to provide variables available in the code .

such as ：

export default {
  define: {
    FOO: 'bar',
  },
};

//  You can get it directly from the page  FOO  Variable , To use 
// console.log(FOO) --> bar

Call mode ：process.env.xxx

Built in define attribute :

process.env.NODE_ENV, The value is development or production
process.env.NODE_ENV === ‘development’ // development environment
process.env.NODE_ENV === ‘production’ // Production environment

Apply to document.ejs

stay document.ejs in , call process.env , Get the current is Shell All environment variables of , contain .NODE_ENV. But I can't get umi define Properties in .
here , Must pass context.config To get define .
context.config Can get .umi.js All variables of the configuration file .

Call mode ：<%=context.config.xxx %>