Recently, I struggled a bit to figure out a way to access Azure-Pipeline Variables in Node.js JavaScript/TypeScript project. However, it is easy.

.yml Pipeline code

- task: Npm@1
  displayName: "Run project"
  env:
    MyVariableName: $(MYVARIABLENAME)  // this is pipeline variable name, in Capital letters
  inputs:
    commands: 'custom'
    CustomCommand: 'run test'

npm Package

install package string-replace-loader

TypeScript/JavaScript File

Create a file with any name “test.ts”

test.ts

const test = () => {
    
    const myVariable = "My-Variable";

};

Setup webpack.config.js

 module: {
    rules: [
      {
        test: /test\.ts$/,
        loader: 'string-replace-loader',
        options: {
          search: 'My-Variable',
          replace: process.env['MyVariableName']  // from .yml env
        }
      }
    ]
  }
}

Finally

"scripts" :{
    "test": "webpack --config webpack.config.js"
}