Can i add conditional events on svelte components? - events

Question

is it possible for an event to be fired on a condition defined in the parent component ?
I have an input component where i want to capture the input.. sometimes, but most of the time i dont want the event to fire
//App.html
<Input on:inputData="doStuff(event)" fireEvent=true />
//Input.html
<input bind:value=value (fireEvent ? on:keyup='fire("inputData", { value })' : false )/>
What happens currently is that fireEvent is ignored and on:keyup allways fires
UPDATE
I changed the keyup into a function call where i checked the parameter before firing the event, it works but its kinda wacky
//App.html
<Input on:inputData='doStuff(event.value)' fireEvent={true} />
...
methods: {
doStuff(text) {
console.log('here is the stuff', text);
}
//Input.html
<input bind:value=value on:keyup='setData({ value })'/>
...
methods: {
setData(text) {
if(this.get().fireEvent) {
this.fire("inputData", text)
}
}
}
Anyone got a prettier solution to this problem ?

Answer 1

Very late to the party, but I had a similar problem and ended up solving it with an action. For mine, I needed to attach a click listener to a button only if a certain condition was truthy. A more generic example could be:
<button use:conditionalEvent({condition: foo, event: 'click', callback: bar})>...</button>
...
function conditionalEvent(node, {condition, event, callback}) {
if (condition) {
node.addEventListener(event, callback);
}
return {
destroy() {
node.removeEventListener(event, callback)
}
}
}
The markup could be less verbose if it was only for a single callback or event type, but you get the point.
If the condition can change with user input, you can also return an update function:
function changingCondition(node, {condition, event, callback}) {
function update(condition) {
if (condition) {
node.addEventListener(event, callback);
} else {
node.removeEventListener(event, callback);
}
}
update(condition);
return {
update,
destroy() {
node.removeEventListener(event, callback)
}
}
}
And the update will run whenever condition changes.

Answer 2

I dont know why i didnt think of this but this is excatly what onupdate is for
//App.html
<Input on:inputData='doStuff(event.value)' fireEvent={true} />
...
methods: {
doStuff(text) {
console.log('here is the stuff', text);
}
//Input.html
<input bind:value=value />
...
onupdate({ changed, current, previous }) {
if(this.get().fireEvent) {
this.fire("inputData", current)
}

Answer 3

I tried the following and it worked. note the lower case 'fireevent'. The capital letter threw it off. Naturally you'd have to change it to on:inputData etc.
methods: {
test(evt) {
console.log('evt.fireEvent', evt.target.getAttributeNode("fireEvent").value);
if (evt.target.getAttributeNode("fireevent").value && evt.target.getAttributeNode("fireevent").value=="true")
console.log('do the happy dance');
else
console.log('do NOTHING');
}
}
<button on:click="test(event)" fireevent="false">Test</button>