Error handling and retries with AJAX requests in Knockout

Question

ICSM Computer · Answer

Handling errors and retries in AJAX requests is crucial for making your Knockout.js apps robust, especially when dealing with flaky connections or server issues. Let’s go over a clean and reusable way to do this using
observables, retry logic, and error UI feedback.and 
Basic Setup with Observables
function DataViewModel() {
  const self = this;
  self.data = ko.observable(null);
  self.error = ko.observable('');
  self.loading = ko.observable(false);
  self.retryCount = ko.observable(0);
  const MAX_RETRIES = 3;
  self.loadData = function () {
    self.loading(true);
    self.error('');
    $.ajax({
      url: '/api/data',
      method: 'GET',
      success: function (response) {
        self.data(response);
        self.retryCount(0); // reset retry count on success
      },
      error: function (xhr, status, err) {
        self.retryCount(self.retryCount() + 1);
        if (self.retryCount() andlt; MAX_RETRIES) {
          console.warn(`Retry ${self.retryCount()}...`);
          setTimeout(self.loadData, 1000); // retry after 1s
        } else {
          self.error("Failed to load data after several attempts.");
        }
      },
      complete: function () {
        self.loading(false);
      }
    });
  };
  self.retryNow = function () {
    self.retryCount(0);
    self.loadData();
  };
  self.loadData(); // Initial load
}
ko.applyBindings(new DataViewModel());
HTML Template Example
andlt;div data-bind="if: loading"andgt;
  andlt;pandgt;🔄 Loading data...andlt;/pandgt;
andlt;/divandgt;
andlt;div data-bind="if: error"andgt;
  andlt;p style="color: red;" data-bind="text: error"andgt;andlt;/pandgt;
  andlt;button data-bind="click: retryNow"andgt;Retryandlt;/buttonandgt;
andlt;/divandgt;
andlt;div data-bind="if: data"andgt;
  andlt;pre data-bind="text: ko.toJSON(data, null, 2)"andgt;andlt;/preandgt;
andlt;/divandgt;
Best Practices
Tip
Why
Use .retryCount()
To control retry attempts
setTimeout()
Avoid hammering the server immediately
self.error()
Show user-friendly messages
Wrap $.ajax()
Use a custom utility function for reuse
Optional: Create a Reusable ajaxWithRetry Utility
function ajaxWithRetry(options, maxRetries = 3, delay = 1000) {
  let attempts = 0;
  function attemptAjax(resolve, reject) {
    $.ajax({
      ...options,
      success: resolve,
      error: function (xhr, status, err) {
        if (++attempts andlt; maxRetries) {
          setTimeout(() =andgt; attemptAjax(resolve, reject), delay);
        } else {
          reject(err);
        }
      }
    });
  }
  return new Promise((resolve, reject) =andgt; {
    attemptAjax(resolve, reject);
  });
}
Now use it like this in your ViewModel:
self.loadData = function () {
  self.loading(true);
  self.error('');
  ajaxWithRetry({ url: '/api/data', method: 'GET' })
    .then(data =andgt; self.data(data))
    .catch(() =andgt; self.error("Failed after multiple retries"))
    .finally(() =andgt; self.loading(false));
};
and

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Error handling and retries with AJAX requests in Knockout

ICSM Computer

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1 Answers

Basic Setup with Observables

HTML Template Example

Best Practices

Optional: Create a Reusable `ajaxWithRetry` Utility

Liked By

Tip	Why
Use `.retryCount()`	To control retry attempts
`setTimeout()`	Avoid hammering the server immediately
`self.error()`	Show user-friendly messages
Wrap `$.ajax()`	Use a custom utility function for reuse