If you want to deal with both the data formats, the most straight forward way to do it is checking whether the data.StoreVisitGraphCount.list is an Array or an Object. Taking a cure from the question: How to check if a JSON response element is an array? , the most reliable way to do it is:

function isArray(what) {
    return Object.prototype.toString.call(what) === '[object Array]';
}

Then your code would read:

d3.json(..., function(error, data) {
  if (!isArray(data.StoreVisitGraphCount.list)) {
    data.StoreVisitGraphCount.list = [ data.StoreVisitGraphCount.list ];
  }

  data.StoreVisitGraphCount.list.forEach(function(d) {
    d.date = parseDate(d.date);
    d.count = +d.count;
  });
});

However, that is not a very consistent API design. If the API is in your control (you are running the service from localhost), then consider changing it to be consistent and return a list in every case.

If you want to deal with both the data formats, the most straight forward way to do it is checking whether the data.StoreVisitGraphCount.list is an Array or an Object. Taking a cure from the question: How to check if a JSON response element is an array? , the most reliable way to do it is:

function isArray(what) {
    return Object.prototype.toString.call(what) === '[object Array]';
}

Then your code would read:

d3.json(..., function(error, data) {
  if (!isArray(data.StoreVisitGraphCount.list)) {
    data.StoreVisitGraphCount.list = [ data.StoreVisitGraphCount.list ];
  }

  data.StoreVisitGraphCount.list.forEach(function(d) {
    d.date = parseDate(d.date);
    d.count = +d.count;
  });
});

However, that is not a very consistent API design. If the API is in your control (you are running the service from localhost), then consider changing it to be consistent and return a list in every case.

If you want to deal with both the data formats, the most straight forward way to do it is checking whether the data.StoreVisitGraphCount.list is an Array or an Object. Taking a cure from the question: How to check if a JSON response element is an array? , the most reliable way to do it is:

function isArray(what) {
    return Object.prototype.toString.call(what) === '[object Array]';
}

Then your code would read:

d3.json(..., function(error, data) {
  if (!isArray(data.StoreVisitGraphCount.list)) {
    data.StoreVisitGraphCount.list = [ data.StoreVisitGraphCount.list ];
  }

  data.StoreVisitGraphCount.list.forEach(function(d) {
    d.date = parseDate(d.date);
    d.count = +d.count;
  });
});

However, that is not a very consistent API design. If the API is in your control (you are running the service from localhost), then consider changing it to be consistent and return a list in every case.

Also, I would consider this more of a javascript question than a d3.js question.

If you want to deal with both the data formats, the most straight forward way to do it is checking whether the data.StoreVisitGraphCount.list is an Array or an Object. Taking a cure from the question: How to check if a JSON response element is an array? , the most reliable way to do it is:

function isArray(what) {
    return Object.prototype.toString.call(what) === '[object Array]';
}

Then your code would read:

d3.json(..., function(error, data) {
  if (!isArray(data.StoreVisitGraphCount.list)) {
    data.StoreVisitGraphCount.list = [ data.StoreVisitGraphCount.list ];
  }

  data.StoreVisitGraphCount.list.forEach(function(d) {
    d.date = parseDate(d.date);
    d.count = +d.count;
  });
});

However, that is not a very consistent API design. If the API is in your control (you are running the service from localhost), then consider changing it to be consistent and return a list in every case.