How to Troubleshoot Angular "10 $digest() iterations reached" Error

as Ven said, you are either returning different (not identical) objects on each $digest cycle, or you are altering the data too many times.

The fastest solution to figure out which part of your app is causing this behavior is:

1. remove all suspicious HTML - basically remove all your html from the template, and check if there are no warnings
2. if there are no warnings - add small parts of the html you removed and check if the problem is back
3. repeat step 2 until you get a warning - you will figure out which part of your html is responsible for the problem
4. investigate further - the part from step 3 is responsible for either mutating the objects on the $scope or is returning non-identical objects on each $digest cycle.
5. if you still have $digest iteration warnings after step 1, than you are probably doing something very suspicious. Repeat the same steps for parent template/scope/controller

You also want to make sure you are not altering the input of your custom filters

Keep in mind, that in JavaScript there are specific types of objects that don't behave like you would normally expect:

new Boolean(true) === new Boolean(true) // false
new Date(0) == new Date(0) // false
new String('a') == new String('a') // false
new Number(1) == new Number(1) // false
[] == [] // false
new Array == new Array // false
({})==({}) // false

Usually that happens when you're returning a different object every time.

For example, if you use this in a ng-repeat:

$scope.getObj = function () {
  return [{a: 1}, {b: 2}];
};

You're going to get this error message because Angular tries to have the "stability" and will execute the function until it returns the same result 2 times (comparing with ===), which in our case will never return true because the function always returns a new object.

console.log({} === {}); // false. Those are two different objects!

In this case, you can fix it by storing the object in scope directly, e.g.

$scope.objData = [{a: 1}, {b: 2}];
$scope.getObj = function () {
  return $scope.objData;
};

That way you're always returning the same object!

console.log($scope.objData === $scope.objData); // true (a bit obvious...)

(You should never encounter that, even on complex applications).

Update: Angular has added some more in-depth explanation on their website.

Just wanted to throw this solution in here, hopefully it'll help others. I was getting this iteration problem because I was iterating over a generated property which was making a new object every time it was called.

I fixed it by caching the generated object the first time it was requested, and then always returning the cache if it existed. A dirty() method was also added, which would destroy the cached results as needed.

I had something like this:

function MyObj() {
    var myObj = this;
    Object.defineProperty(myObj, "computedProperty" {
        get: function () {
            var retObj = {};

            return retObj;
        }
    });
}

And here's with the solution implemented:

function MyObj() {
    var myObj = this,
        _cached;
    Object.defineProperty(myObj, "computedProperty" {
        get: function () {
            if ( !_cached ) {
                _cached = {};
            }

            return _cached;
        }
    });

    myObj.dirty = function () {
        _cached = null;
    }
}