Filtering and ignoring changes

Palindrom deeply observes changes made to the palindrom.obj object and converts them to patches. If you have a need to ignore some kind of changes, there are two ways to do it. Either make the changes in non-enumerable property or use a filtering function to ignore changes made in the enumerable properties.

Palindrom only generates patches for the enumerable properties of palindrom.obj and its subtrees. To create a part of the tree that is invisible for Palindrom's patch collection, define a non-enumerable property.

Assuming your Palindrom instance is instantiated and your palindrom.obj is ready, you can create a non-enumerable object child in palindrom.obj and use it as a local non-observed store for your needs.


Object.defineProperty(palindrom.obj, "myLocalNonSyncedObject", {
    enumerable: false,
    value: {}

Now palindrom.obj.myLocalNonSyncedObject is an object this is not observed for patch generation. This is ideal for keeping client-side related information (eg: div height, or something like isModalWarningDisplayed = true).


palindrom.obj.myLocalNonSyncedObject.divHeight = 50;

... does not generate a patch.

Note: In most cases, the added property is recommended to be an object.*

*Note: You should not replace the value of the non-enumerable property after it has been defined. Otherwise Palindrom will still detect the change. If you want to modify the unobserved values, you should declare the non-enumerable property as an object and only modify its children.

2. By extending Palindrom#filterLocalChange

You can discard a generated patch by extending Palindrom.filterLocalChange function. This function accepts a JSON Patch operation and either returns it or returns a falsy value. Returning a falsy value results in ignoring this operation.


const palindrom = new Palindrom({ remoteUrl: window.location.href });

var old = palindrom.filterLocalChange;
palindrom.filterLocalChange = function(operation) {
    operation =, operation); //make sure you don't overwrite other filters
    if (operation && !operation.path.startsWith('$')) {
        return operation;
// use palindrom.obj
palindrom.obj.$someProperty = 'new value'; // this change will be ignored and will not reach the server

You can also pass filterLocalChange to Palindrom constructor as in:

const palindrom = new Palindrom({ remoteUrl: window.location.href, filterLocalChange: op => !op.path.startsWith('$') && op });