Return array values from function for use in next function

Question

I have this function:

getSlaves: function() {
  fs.readFile('/etc/hosts', function(err, data) {
    var array = data.toString().split("\n");
    for(i in array) {
      if (array[i].indexOf('slave') > -1){
        var workerNo = array[i].slice(-1);
        var ip = array[i].split(" ");
        console.log(ip);
      }
    }
  });
}

At present it writes this to console:

[ '192.168.11.1', 'slave1' ]
[ '192.168.11.2', 'slave2' ]
[ '192.168.11.3', 'slave3' ]

I want this to return so I can use it in another function. I've tried adding return(ip) and callback(ip) to the method but that doesn't work.How can I return these values so they can be used by an different function?

have you tried declaring the variable outside of the function so that it is global, then setting it in the function? — , Mar 30 '18 at 13:24
Possible duplicate of [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — vibhor1997a, Mar 30 '18 at 13:27
You need to build a list of `ip` values and return them all at once. Or use function generator and yield the values (<-- not sure if this is a good idea). — user202729, Mar 30 '18 at 13:27

score 0 · Answer 1 · answered Mar 30 '18 at 13:35

Way you can pass the array of ips into a callback

function getSlaves(callback) {
    if (err) {
        callback(err);
    }
    else {
        fs.readFile('/etc/hosts', function (err, data) {
            var array = data.toString().split("\n");
            let data = [];//to store ips
            for (i in array) {
                if (array[i].indexOf('slave') > -1) {
                    var workerNo = array[i].slice(-1);
                    var ip = array[i].split(" ");
                    data.push(ip);
                }
            }
            callback(undefined, rarr);
        });
    }
}

How do you access the array

function yourFunc(){
    getSlaves((err,data)=>{
        if(err){
            console.log(err);
        }
        else{
            console.log(data);
        }
    });
}

Return array values from function for use in next function

1 Answers1