Adding real-time value to AngularJS directives without triggering reassessment

Question

Adding real-time value to AngularJS directives without triggering reassessment

Seeking guidance on utilizing an AngularJS directive as an HTML element, with the intention to provide it two values. One will be fetched by iterating through a collection, while the other will be derived from that value:

<mydirective myval="val" mymagic="getMagic(val)" ng-repeat="val in values" />

Everything functions correctly when the getMagic(val) function consistently returns the same result. However, since the values are Arrays that change with each call, it leads to an

[$rootScope:infdig] 10 $digest() iterations reached. Aborting!

error. Click here to view a fiddle of my scenario (it works if the function is defined like it is in the commented line).

Is there a method to prevent reevaluation or "watching" of the mymagic parameter? The goal is for the value to update only when the values collection changes, without calling the function unnecessarily.

How can I achieve this?

javascript angularjs

Answer 1

Answer №1

Give this a try

(NEW JSFIDDLE)

https://jsfiddle.net/yogeshgadge/6T8mr/6/

Take note of the update - your getMagic() function was being called multiple times due to the values returned triggering changes, leading to an infinite digest loop.

app.directive("mydirective", function () {
    return {
        restrict: "E",
        transclude: false,
        scope: {
            myval: "=",  
            mymagic: "&" //passing the function
        },
        template: "<li>{{myval}} -- {{mymagic()}}</li>", 
        ///mymagic() executing this function here 
        replace: true
    };
});

Answer 2

Give this a try

(NEW JSFIDDLE)

https://jsfiddle.net/yogeshgadge/6T8mr/6/

Take note of the update - your getMagic() function was being called multiple times due to the values returned triggering changes, leading to an infinite digest loop.

app.directive("mydirective", function () {
    return {
        restrict: "E",
        transclude: false,
        scope: {
            myval: "=",  
            mymagic: "&" //passing the function
        },
        template: "<li>{{myval}} -- {{mymagic()}}</li>", 
        ///mymagic() executing this function here 
        replace: true
    };
});

Answer 3

Answer №2

It seems like your concern revolves around the repeated invocation of getMagic(val) during the rendering process of the page. The reason behind this behavior is the $digest cycle running multiple times to ensure complete page rendering, which is standard protocol. For further details, refer to the Angular scope guide.

To address this issue, you can generate the magic numbers within the controller and link them to a scope. Subsequently, whenever there are changes in the array or magic numbers, trigger $scope.$apply() explicitly.

The following approach might be suitable:

app.controller('Controller',
    function ($scope) {
        var getMagic = function(val){
            return val + 1;
        };
        $scope.values = [3,7,1,2, 100];
        $scope.magic = recalculate();

        // EDIT: recalculating $scope.magic every time $scope.values changes:
        function recalculate() {
            return $scope.values.map(getMagic);
        }
        $scope.$on('something-changed', recalculate();
    });

Remember to manually invoke $digest() each time there are modifications to either the values or magic arrays. While this method may lack the elegance of using a $watch() expression, it offers better performance by minimizing unnecessary reevaluation of the magic array.

Answer 4

It seems like your concern revolves around the repeated invocation of getMagic(val) during the rendering process of the page. The reason behind this behavior is the $digest cycle running multiple times to ensure complete page rendering, which is standard protocol. For further details, refer to the Angular scope guide.

To address this issue, you can generate the magic numbers within the controller and link them to a scope. Subsequently, whenever there are changes in the array or magic numbers, trigger $scope.$apply() explicitly.

The following approach might be suitable:

app.controller('Controller',
    function ($scope) {
        var getMagic = function(val){
            return val + 1;
        };
        $scope.values = [3,7,1,2, 100];
        $scope.magic = recalculate();

        // EDIT: recalculating $scope.magic every time $scope.values changes:
        function recalculate() {
            return $scope.values.map(getMagic);
        }
        $scope.$on('something-changed', recalculate();
    });

Remember to manually invoke $digest() each time there are modifications to either the values or magic arrays. While this method may lack the elegance of using a $watch() expression, it offers better performance by minimizing unnecessary reevaluation of the magic array.

Adding real-time value to AngularJS directives without triggering reassessment

Answer №1

Answer №2

Similar questions

What methods can be used to extend the distance measurement with the help of Google Maps

What steps can you take to resolve the issue of FirebaseError: When collection() is expected to be a CollectionReference, DocumentReference, or FirebaseFirestore?

What is the reason for adding CSS styles to a JavaScript file without importing them?

Nuxt middleware failing to verify user's logged-in status

Obtain saved browsing history in HTML5 with the use of JavaScript

Duplicating an Angular 2 reactive form without retaining the original reference

Leveraging Variables within my .env Configuration

Issue with React component not displaying in the browser.Here are some

Transferring data files through an ajax-based form submission

"Stuck in a Standstill: Express/React Commit

What steps do I need to take to execute a browserify-ed application in NodeJS?

Does Javacc have a capability to generate JavaScript code as an output?

Guidelines for transferring JavaScript array data to a csv file on the client side

Facing a node.js installation issue on Windows 10 while using Visual Studio Code (VS

Updating the component's state based on the server response

How can you add draggable functionality to a Bootstrap dropdown menu?

Reload the MEN stack webpage without the need to reload the entire page

Creating a process to produce a random number and send it directly to an automated email

Send the form to the webpage and display various div elements based on the entered information

ESLint encountered an error while attempting to load the configuration "next/babel" for extension