I am new in Protractor Automaton also able to execute test using npm test but don't know why we are using any other build tools like gulp, karma and grunt. i don't know which one is better for script run. we have lots of test script but it's typically manage
package.json
"scripts": {
"test": "node ./node_modules/protractor/node_modules/webdriver-manager update && protractor config/conf.js"
},
You can think gulp and grunt is a tool like maven in Java world. There are many plugins for them, like plugins for maven to help to compile, minify, copy/move files and so on.
In additionally, you can split those take into separate files to make them can be re-used.
For scripts in package.json, you can't make it complex, like if/else or more complex logic or reuse. But gulp and 'grunt' supports.