require not working with npm start command

I’m taking my firsts steps with js and node today, so I’ve created the following script:

var fs = require('fs');

function callBack(){}
fs.writeFile('./abc.txt', "My text", callBack);

Very simple script… So when I run it in my terminal with node app.js it works fine, but when I try to run it with npm start it produces the following error:

Line: 1
Error: Expected object
Code: 800A138F

Also, my package.json looks like it:

{
    "name": "first_app",
    "version": "1.0.0",
    "private": true,
    "requires": true,

    "scripts": {
        "start": "app.js"
    },
    "dependencies": {
        "fs": "^0.0.1-security"
    }
}

Why am I getting this error and how to solve it?

>Solution :

Try this:

"scripts": {
    "start": "node app.js"
},