How to read data from file, pass it to another function and return the return value of the function?

Question

I'm trying to return arr when final() is called....

  function final(){
        var arr;
        fs.readFile("/my/path/", 'utf8' ,(err, data) => {
            arr = parsing(data);
            arr.splice(-1,1);


      });
        return arr;
    }

It keeps returning undefined. Even though arr inside the readFile brackets gives me an array...

The possible duplicate discusses printing whereas I need a value to use somewhere else. How can I use the value arr in another function/module?

Answer 1

readFile is async function you need to do this

function final(){
        var arr;
        fs.readFile("/my/path/", 'utf8' ,(err, data) => {
            arr = parsing(data);
            arr.splice(-1,1);
            return arr;
        });

}

Answer 2

or pass a callback function to final function

function callback(arr) {
//do something with arr
}

function final(callback) {
    var arr;
    fs.readFile("/my/path/", 'utf8' ,(err, data) => {
        arr = parsing(data);
        arr.splice(-1,1);
        callback(arr);
    });
} 

As @Farhan Yassen's answer won't result correct behavior due to the async nature.

And also, you can always use synchronous version of the readFile with readFileSync