I am not allowed to answer questions yet, but I feel that since this issue has taken me some days to resolve, I should post the solution the only way I can - as a question.
If you have a better solution then please include that in your reply.
Until an element is rendered it is not in the DOM so if you add an event listener to the element in your code you will get an error (element value null).
But you can add a listener to the root element, which is always there. WHen the event is triggered you can then retrieve the className and ID of the element involved in your event-handler.
Code:
var rootElement = document.getElementById('root');
console.log(rootElement);
rootElement.addEventListener('click', rootElementClicked);
console.log('event listener added to root element');
function rootElementClicked(event) {
event.preventDefault();
const { name, value } = event.target;
console.log("Root element clicked with [" + event.target.className, event.target.id);
}
/code
So, the event-listener is app-wide, so a click anywhere will call the event-handler function. Then in the code for that function, the element class and ID will tell you what was clicked.
Note the event.preventDefault(); line - it prevents a refresh of the web page, otherwise the target class & ID are returned as "undefined"
In React you shouldn't need to addEventListener manually since you can use onClick. However if you would like to manually attach click handler on an HTML element in React you can use React Ref. If you pass a ref object to React with <div ref={myRef} /> React will set its .current property to the corresponding DOM node whenever that node changes.
Example: https://codesandbox.io/s/react-hooks-useref-xfvlb
const App = () => {
const elementRef = useRef();
useEffect(() => {
elementRef.current.addEventListener('click', handleOnClick);
},[elementRef])
const handleOnClick = () => {
alert("click")
}
return (
<div className="App">
<div ref={elementRef}>
click on me
</div>
</div>
);
}
I've read through the Ractive Documentation and I'm scratching my head a bit, because it seems like the default events initialization option allows me to do something - create new eventtypes - far more complex than what i need but conversely, there's no hook for the simpler, (more common?) task of defining default events
Could someone advise on how to provide global events that could be fired for traditional DOM events?
Example:
I have a 3 Component application page. I want to define a getOptions event, such that any <select on-click='getOptions'>...</select> will be handled by the same function. I don't want to have to define that function in each component.
My intuition would have been to do the following:
Ractive.events['getOptions'] = function(event){
//logic for getting the options for the value in event.keypath
}
or, if i wanted a true default that could be overridden...
Ractive.default.events['getOptions'] = function(event){
//logic for getting the options for the value in event.keypath
}
but my understanding of the documentation, is that Ractive.events and Ractive.default.events do not provide this, but rather provide a way to define new event plugins, that depend on a separate mechanism for getting fired:
Ractive.events.getoptions = function(node,fire){
//here goes logic for interacting with DOM event listeners, etc
}
//and then i would need to do this
ractive = Ractive.extend({...});
ractive.on('someOtherEventName',function(event){
//logic for getting the options for the value in event.keypath
});
//and then I could do this...
<select on-getoptions='someOtherEventName'>...</select>
but what would fire the getoptions in this case - from the template, rather than js ractive.fire()?
Would something like <select on-getoptions='someOtherFunction' on-click=getoptions>...</select> work? That seems very strange to me. Do I understand the concept correction? If not, what am i missing?
Is there a simple way to achieve the first example?
Ractive.events refers to custom events for mediating between the dom and the template:
Ractive.events.banana = function( node, fire ) { ... };
<div on-banana="doSomething()"/>
The handler for the event can either be the name of an event to fire, or a method on the component instance.
In your case, I think defining a method on the Ractive.prototype would be the best way to have a common handler:
Ractive.prototype.getOptions = function( /* pass in arguments */ ){
// and/or this.event will give you access
// to current event and thus context
// you can also override this method in components and
// call this base method using this._super(..)
}
// now any ractive instance can use:
<select on-click="getOptions(data)">...</select>
An event based approach usually entails letting the root instance or common parent in the view hierarchy handle same event across child components:
var app = new Ractive({
template: "<componentA/><componentB/>",
oninit(){
this.on( '*.getOptions', ( event, arg ) => {
// any child component (at any depth)
// that fires a "getOptions" event will
// end up here
});
}
});
// in component A or B:
<select on-click="getOptions">...</select>
UPDATE: If you wanted to assign an event handler to the prototype, so in essence every component is pre-wired to handle an event of a set name, you could do:
Ractive.prototype.oninit = function(){
this.on( 'getOptions', ( event ) => {
// handle any "getOptions" event that happens in the instance
});
}
Just be aware that you must call this._super(); in any component in which you also implement oninit:
var Component = Ractive.extend({
oninit() {
// make sure we call the base or event listener won't happen!
this._super();
// do this component instances init work...
}
}
How should one access state (just state, not the React State) of child components in React?
I've built a small React UI. In it, at one point, I have a Component displaying a list of selected options and a button to allow them to be edited. Clicking the button opens a Modal with a bunch of checkboxes in, one for each option. The Modal is it's own React component. The top level component showing the selected options and the button to edit them owns the state, the Modal renders with props instead. Once the Modal is dismissed I want to get the state of the checkboxes to update the state of the parent object. I am doing this by using refs to call a function on the child object 'getSelectedOptions' which returns some JSON for me identifying those options selected. So when the Modal is selected it calls a callback function passed in from the parent which then asks the Modal for the new set of options selected.
Here's a simplified version of my code
OptionsChooser = React.createClass({
//function passed to Modal, called when user "OK's" their new selection
optionsSelected: function() {
var optsSelected = this.refs.modal.getOptionsSelected();
//setState locally and save to server...
},
render: function() {
return (
<UneditableOptions />
<button onClick={this.showModal}>Select options</button>
<div>
<Modal
ref="modal"
options={this.state.options}
optionsSelected={this.optionsSelected}
/>
</div>
);
}
});
Modal = React.createClass({
getOptionsSelected: function() {
return $(React.findDOMNode(this.refs.optionsselector))
.find('input[type="checkbox"]:checked').map(function(i, input){
return {
normalisedName: input.value
};
}
);
},
render: function() {
return (
//Modal with list of checkboxes, dismissing calls optionsSelected function passed in
);
}
});
This keeps the implementation details of the UI of the Modal hidden from the parent, which seems to me to be a good coding practice. I have however been advised that using refs in this manner may be incorrect and I should be passing state around somehow else, or indeed having the parent component access the checkboxes itself. I'm still relatively new to React so was wondering if there is a better approach in this situation?
Yeah, you don't want to use refs like this really. Instead, one way would be to pass a callback to the Modal:
OptionsChooser = React.createClass({
onOptionSelect: function(data) {
},
render: function() {
return <Modal onClose={this.onOptionSelect} />
}
});
Modal = React.createClass({
onClose: function() {
var selectedOptions = this.state.selectedOptions;
this.props.onClose(selectedOptions);
},
render: function() {
return ();
}
});
I.e., the child calls a function that is passed in via props. Also the way you're getting the selected options looks over-fussy. Instead you could have a function that runs when the checkboxes are ticked and store the selections in the Modal state.
Another solution to this problem could be to use the Flux pattern, where your child component fires off an action with data and relays it to a store, which your top-level component would listen to. It's a bit out of scope of this question though.
What I am trying to implement is basically a "on ng repeat finished rendering" handler. I am able to detect when it is done but I can't figure out how to trigger a function from it.
Check the fiddle:http://jsfiddle.net/paulocoelho/BsMqq/3/
JS
var module = angular.module('testApp', [])
.directive('onFinishRender', function () {
return {
restrict: 'A',
link: function (scope, element, attr) {
if (scope.$last === true) {
element.ready(function () {
console.log("calling:"+attr.onFinishRender);
// CALL TEST HERE!
});
}
}
}
});
function myC($scope) {
$scope.ta = [1, 2, 3, 4, 5, 6];
function test() {
console.log("test executed");
}
}
HTML
<div ng-app="testApp" ng-controller="myC">
<p ng-repeat="t in ta" on-finish-render="test()">{{t}}</p>
</div>
Answer:
Working fiddle from finishingmove: http://jsfiddle.net/paulocoelho/BsMqq/4/
var module = angular.module('testApp', [])
.directive('onFinishRender', function ($timeout) {
return {
restrict: 'A',
link: function (scope, element, attr) {
if (scope.$last === true) {
$timeout(function () {
scope.$emit(attr.onFinishRender);
});
}
}
}
});
Notice that I didn't use .ready() but rather wrapped it in a $timeout. $timeout makes sure it's executed when the ng-repeated elements have REALLY finished rendering (because the $timeout will execute at the end of the current digest cycle -- and it will also call $apply internally, unlike setTimeout). So after the ng-repeat has finished, we use $emit to emit an event to outer scopes (sibling and parent scopes).
And then in your controller, you can catch it with $on:
$scope.$on('ngRepeatFinished', function(ngRepeatFinishedEvent) {
//you also get the actual event object
//do stuff, execute functions -- whatever...
});
With html that looks something like this:
<div ng-repeat="item in items" on-finish-render="ngRepeatFinished">
<div>{{item.name}}}<div>
</div>
Use $evalAsync if you want your callback (i.e., test()) to be executed after the DOM is constructed, but before the browser renders. This will prevent flicker -- ref.
if (scope.$last) {
scope.$evalAsync(attr.onFinishRender);
}
Fiddle.
If you really want to call your callback after rendering, use $timeout:
if (scope.$last) {
$timeout(function() {
scope.$eval(attr.onFinishRender);
});
}
I prefer $eval instead of an event. With an event, we need to know the name of the event and add code to our controller for that event. With $eval, there is less coupling between the controller and the directive.
The answers that have been given so far will only work the first time that the ng-repeat gets rendered, but if you have a dynamic ng-repeat, meaning that you are going to be adding/deleting/filtering items, and you need to be notified every time that the ng-repeat gets rendered, those solutions won't work for you.
So, if you need to be notified EVERY TIME that the ng-repeat gets re-rendered and not just the first time, I've found a way to do that, it's quite 'hacky', but it will work fine if you know what you are doing. Use this $filter in your ng-repeat before you use any other $filter:
.filter('ngRepeatFinish', function($timeout){
return function(data){
var me = this;
var flagProperty = '__finishedRendering__';
if(!data[flagProperty]){
Object.defineProperty(
data,
flagProperty,
{enumerable:false, configurable:true, writable: false, value:{}});
$timeout(function(){
delete data[flagProperty];
me.$emit('ngRepeatFinished');
},0,false);
}
return data;
};
})
This will $emit an event called ngRepeatFinished every time that the ng-repeat gets rendered.
How to use it:
<li ng-repeat="item in (items|ngRepeatFinish) | filter:{name:namedFiltered}" >
The ngRepeatFinish filter needs to be applied directly to an Array or an Object defined in your $scope, you can apply other filters after.
How NOT to use it:
<li ng-repeat="item in (items | filter:{name:namedFiltered}) | ngRepeatFinish" >
Do not apply other filters first and then apply the ngRepeatFinish filter.
When should I use this?
If you want to apply certain css styles into the DOM after the list has finished rendering, because you need to have into account the new dimensions of the DOM elements that have been re-rendered by the ng-repeat. (BTW: those kind of operations should be done inside a directive)
What NOT TO DO in the function that handles the ngRepeatFinished event:
Do not perform a $scope.$apply in that function or you will put Angular in an endless loop that Angular won't be able to detect.
Do not use it for making changes in the $scope properties, because those changes won't be reflected in your view until the next $digest loop, and since you can't perform an $scope.$apply they won't be of any use.
"But filters are not meant to be used like that!!"
No, they are not, this is a hack, if you don't like it don't use it. If you know a better way to accomplish the same thing please let me know it.
Summarizing
This is a hack, and using it in the wrong way is dangerous, use it only for applying styles after the ng-repeat has finished rendering and you shouldn't have any issues.
If you need to call different functions for different ng-repeats on the same controller you can try something like this:
The directive:
var module = angular.module('testApp', [])
.directive('onFinishRender', function ($timeout) {
return {
restrict: 'A',
link: function (scope, element, attr) {
if (scope.$last === true) {
$timeout(function () {
scope.$emit(attr.broadcasteventname ? attr.broadcasteventname : 'ngRepeatFinished');
});
}
}
}
});
In your controller, catch events with $on:
$scope.$on('ngRepeatBroadcast1', function(ngRepeatFinishedEvent) {
// Do something
});
$scope.$on('ngRepeatBroadcast2', function(ngRepeatFinishedEvent) {
// Do something
});
In your template with multiple ng-repeat
<div ng-repeat="item in collection1" on-finish-render broadcasteventname="ngRepeatBroadcast1">
<div>{{item.name}}}<div>
</div>
<div ng-repeat="item in collection2" on-finish-render broadcasteventname="ngRepeatBroadcast2">
<div>{{item.name}}}<div>
</div>
The other solutions will work fine on initial page load, but calling $timeout from the controller is the only way to ensure that your function is called when the model changes. Here is a working fiddle that uses $timeout. For your example it would be:
.controller('myC', function ($scope, $timeout) {
$scope.$watch("ta", function (newValue, oldValue) {
$timeout(function () {
test();
});
});
ngRepeat will only evaluate a directive when the row content is new, so if you remove items from your list, onFinishRender will not fire. For example, try entering filter values in these fiddles emit.
If you’re not averse to using double-dollar scope props and you’re writing a directive whose only content is a repeat, there is a pretty simple solution (assuming you only care about the initial render). In the link function:
const dereg = scope.$watch('$$childTail.$last', last => {
if (last) {
dereg();
// do yr stuff -- you may still need a $timeout here
}
});
This is useful for cases where you have a directive that needs to do DOM manip based on the widths or heights of the members of a rendered list (which I think is the most likely reason one would ask this question), but it’s not as generic as the other solutions that have been proposed.
I'm very surprised not to see the most simple solution among the answers to this question.
What you want to do is add an ngInit directive on your repeated element (the element with the ngRepeat directive) checking for $last (a special variable set in scope by ngRepeat which indicates that the repeated element is the last in the list). If $last is true, we're rendering the last element and we can call the function we want.
ng-init="$last && test()"
The complete code for your HTML markup would be:
<div ng-app="testApp" ng-controller="myC">
<p ng-repeat="t in ta" ng-init="$last && test()">{{t}}</p>
</div>
You don't need any extra JS code in your app besides the scope function you want to call (in this case, test) since ngInit is provided by Angular.js. Just make sure to have your test function in the scope so that it can be accessed from the template:
$scope.test = function test() {
console.log("test executed");
}
A solution for this problem with a filtered ngRepeat could have been with Mutation events, but they are deprecated (without immediate replacement).
Then I thought of another easy one:
app.directive('filtered',function($timeout) {
return {
restrict: 'A',link: function (scope,element,attr) {
var elm = element[0]
,nodePrototype = Node.prototype
,timeout
,slice = Array.prototype.slice
;
elm.insertBefore = alt.bind(null,nodePrototype.insertBefore);
elm.removeChild = alt.bind(null,nodePrototype.removeChild);
function alt(fn){
fn.apply(elm,slice.call(arguments,1));
timeout&&$timeout.cancel(timeout);
timeout = $timeout(altDone);
}
function altDone(){
timeout = null;
console.log('Filtered! ...fire an event or something');
}
}
};
});
This hooks into the Node.prototype methods of the parent element with a one-tick $timeout to watch for successive modifications.
It works mostly correct but I did get some cases where the altDone would be called twice.
Again... add this directive to the parent of the ngRepeat.
Very easy, this is how I did it.
.directive('blockOnRender', function ($blockUI) {
return {
restrict: 'A',
link: function (scope, element, attrs) {
if (scope.$first) {
$blockUI.blockElement($(element).parent());
}
if (scope.$last) {
$blockUI.unblockElement($(element).parent());
}
}
};
})
Please have a look at the fiddle, http://jsfiddle.net/yNXS2/. Since the directive you created didn't created a new scope i continued in the way.
$scope.test = function(){... made that happen.
I have a list of buttons (squares) in HTML like this -
<td><button id="18" ></button></td>
<td><button id="28" ></button></td>
<td><button id="38" ></button></td>
...
Earlier, for each button, I had to put code within the button tag itself to add an event handler, like this -
<button id="18" onclick="squareWasClicked(event)">
function squareWasClicked(event)
{
var element = event.target;
// more code
}
But now I have found out that it is not good practice. So instead, I am trying to add event handlers from within my javascript code. But I don't know how to do that. So far, I have tried this -
function assignEventsToSquares()
{
var i,j;
for(i=1;i<=8;i++)
{
for(j=1;j<=8;j++)
{
var squareID = "" + i + "" + j;
var square = document.getElementById(squareID);
square.onclick = squareWasClicked();
}
}
}
But this simply calls the squareWasClicked() function. So how do I add it as an event handler so that the function will be invoked when the square is clicked? Also, how do I say something like
square.onclick = squareWasClicked(event);
event is not detected in the JavaScript code. Please help.
Use element.addEventListener() (originating from the DOM 2 Events spec). In your case it will be
document.getElementById("18").addEventListener("click", squareWasClicked, false);
square.onclick = squareWasClicked();
This calls your click function and assigns the result to your element's event listener, which isn't what you want. Remove the ()s so that the function itself gets assigned.
Hence, it should look like this
square.onclick = squareWasClicked;