Parsing function only returns undefined instead of array-CodePudding

I can't figure out why my function only returns undefined when it should be returning the array:

function parseData (dataFile){
d3.csv(dataFile).then(function(datapoints) {
    var barLabels = []
    var barData = []
    for (i=0; i < datapoints.length; i  ){
        barLabels.push(Object.values(datapoints[i])[0]);
        barData.push(Object.values(datapoints[i])[1]);
    }
    
    //console.log(barLabels);
    return barLabels;

});
}

console.log(parseData('carbon-footprint-of-apparel-brands-2019.csv'));

CodePudding user response：

You are returning your array from the callback, instead of the parseData function. When your parseData function ends it returns undefined as you have not told it to return anything. Try this:

function parseData (dataFile){
  var barLabels = []
    d3.csv(dataFile).then(function(datapoints) {
        var barData = []
        for (i=0; i < datapoints.length; i  ){
            barLabels.push(Object.values(datapoints[i])[0]);
            barData.push(Object.values(datapoints[i])[1]);
        }
    });

  return barLabels;
}

console.log(parseData('carbon-footprint-of-apparel-brands-2019.csv'));

By pulling the barLabels array outside of the d3.csv call and only pushing to it, you are free to return the array at the end. I also do not know what you are doing with the barData array, but if you are not using it you should remove it.