I have an array of items in a state variable like this.
const [items, setItems] = useState(["item1", "item2", "item3")])
How to replace one item in the array. Below is the method I have used to get it done.
{
let dummy = [...items]
dummy[1] = "items 1.1"
setItems(dummy)
}
But, I am thinking that this is not at all the right way to do this.
Is there any other simplified way to solve this? Thanks in Advance
Your solution is not wrong, but I would add an extra check to make sure that items array contains an element which you wish to change.
let dummy = [...items]
if(typeof dummy[1] == 'undefined') {
// does not exist
}
else {
// does exist
dummy[1] = "items 1.1"
}
setItems(dummy)
Or you can use slice
const idxToChange = 1
setItems([items.slice(0, idxToChange), "items 1.1", items.slice(idxToChange+1, items.length)])
A good explanation of slice
https://www.w3schools.com/jsref/jsref_slice_array.asp
Heres another way to do it. I don't know it's cleaner for you or not.
setItems(items=> items.map((item,idx)=> idx===1?"items 1.1":item));
Related
So while testing my application, I am using a data set. Since the data set has many entries, I am using FlatList to display my list. After creating the list, I want to be able to verify and tap on certain list items. Below, I have attached the code which I am trying to use and it does not work for me. If anyone has a better idea to do this, please let me know.
The approach I think should be taken. I can't think of anything else to make the FlatList scroll and find the item I am looking for.
let isNotFound = true;
while (isNotFound) {
try {
await waitFor(element(by.id((edit_details.index).toString()))).toBeVisible().withTimeout(2000)
isNotFound = false;
} catch (e) {
await element(by.id('credit_history_list')).swipe('up', 'slow', 0.2)
}
}
await element(by.id((edit_details.index).toString())).tap();
It does help scroll the list and it keeps scrolling while it actually finds the entry I am looking for. But the .tap() function does not work. Instead, detox moves on with the next line of code.
Is there a better way to do this?
Thanks in advance!
This sounds spot-on with Detox' whileElement() API.
I think that what you're looking for is this:
const itemId = (edit_details.index).toString();
const listId = 'credit_history_list';
await waitFor(element(by.id(itemId))).toBeVisible()
.whileElement(by.id(listId))
.scroll(100, 'down');
I have a function that runs every time your location changes and I'm trying to set a value in my array when a certain if statement is found true. All I seem to be doing is removing everything from my variable except the value that I am changing. Bad explanation so here is some code...
The data starts like this:
this.state = { selectedItem: [] }
And will change to something like this during normal app use:
selectedItem: [{address: 'Somewhere', latitude: -37.826835, longitude: 144.992030, found: false }]
Here is where I am trying to change the data (This will always run after some data is added):
const newSelectedItem = () => {
let copyB = {...this.state.selectedItem};
copyB.found = true;
return copyB;
};
this.setState({selectedItem: newSelectedItem});
When I try to run:
{this.state.selectedItem.address}
I see the initial value which would be the address "Somewhere" but when my function runs based on location change it disappears. What have I actually done to my data in my above function?
Have I just made it selectedItem: [{found:true}] or something dumb like that?
You were doing fine except for one single thing , in this function :
const newSelectedItem = () => {
let copyB = {...this.state.selectedItem};
copyB.found = true;
return copyB;
};
this.setState({selectedItem: newSelectedItem});
here copyB is now an object , but yours selected Item was an array. So the problem is now selectedItem is now an object when you do setState with newSelctedItem.
SO copyB.found = true; wouldnt evaluate anything rather, try copyB[0].found = true; so there the value will be accessed and return true accordingly.
And when you try to access the state , replace {this.state.selectedItem.address}
with {this.state.selectedItem[0].address} ,
Hope i helps. feel free to ask any doubts.
You can play around with this pen codepen
Well, this is pretty weird since you still get the initial value. There are some problems in your code:
You want to store your variables in a array: It's fine, but the problem comes from the way you retrieve and set your value. Since selectedItem, your {this.state.selectedItem.address} because this is an object destructuring. To do that, you have to destruct your array first, e.g: item = selectedItem[0] or using map, etc... After that, you can try: item.address.
Another problem is from your newSelectedItem. Since let copyB = {...this.state.selectedItem}; will destruct your selectedItem, take all its properties and set to newSelectedItem, it will make your selectedItem become an object, not an array anymore.
If your selectedItem stores only 1 object, so don't use array. This selectedItem will become:
selectedItem: {
address: 'Somewhere',
latitude: -37.826835,
longitude: 144.992030,
found: false
}
It looks like a JSON object, hence you can do: selectedItem.address
In case you still don't get it, place a little debug or a console.log("selectedItem", this.state.selectedItem) to see what happend, and you will find out.
I think in the end I was mapping a function to the data and not the data itself. This was my eventual solution...
const newMyWaypoinys = this.state.myWaypoints.map(a => {
let copyA = {...a};
if (copyA.address === wp.address) {
if (copyA.address === this.state.selectedItem.address) {
this.setState(prevState => ({
selectedItem: {
...prevState.selectedItem,
found: true
}
}))
}
copyA.found = true;
}
return copyA;
});
this.setState({
myWaypoints: newMyWaypoinys,
});
On click, I want to push to array. It works if I manually refresh the Vue extension in the console of Google Chrome but otherwise not
completeStep(index, key) {
let currentSet = index + key
if (this.exercise_completed[index].indexOf(currentSet) === -1) {
this.exercise_completed[index].push(currentSet)
} else {
this.exercise_completed[index].splice(this.exercise_completed[index].indexOf(currentSet), 1)
}
}
maybe try to use this.$forceUpdate(); when you make the change.
https://v2.vuejs.org/v2/api/#vm-forceUpdate
Hope this helps
I would recommend making a key and changing the key on changes in the array. See here:
https://michaelnthiessen.com/force-re-render
I have a 2D array of objects with key/value pairs as a state variable, and I'm trying to use the recommended way of setting/changing state variables, which is to use this.setState({x:y}) instead of directly setting it using this.state.x = y and then forceUpdate(). However, when I try to do that, it gives me an "unexpected token" error.
I basically want to flip a variable from one state to the other, so I'm usng a ternary operator. This code works
toggleBookmark(category, index) {
this.state.menuItems[category][index].bmIcon = (this.state.menuItems[category][index].bmIcon === "bookmark-o") ? "bookmark" : "bookmark-o";
}
This code, which I'd expect to do the same thing, gives an error
toggleBookmark(category, index) {
this.setState({menuItems[category][index].bmIcon: (this.state.menuItems[category][index].bmIcon === "bookmark-o") ? "bookmark" : "bookmark-o"});
}
I thought it might be the ternary operator, so I put the value into a variable and tried setting the state variable with that, but it still gives the same error.
toggleBookmark(category, index) {
var iconText = (this.state.menuItems[category][index].bmIcon === "bookmark-o") ? "bookmark" : "bookmark-o";
this.setState({menuItems[category][index].bmIcon: iconText});
}
Am I doing something wrong? Is what I want to do possible with setState()?
In Javascript, you cannot use an expression as a key for an object when creating that object inline.
The problem here is that you have done {menuItems[category][index].bmIcon: iconText} which will throw a syntax error.
If you want a quick way to solve this, you may create the object first, then assign the value to that key like this:
var state = {};
state[menuItems[category][index].bmIcon] = iconText;
this.setState(state);
It's worth noting however that ES6 Provides a sugar for doing this, and there is another answer here that might provide more insight
How do I create a dynamic key to be added to a JavaScript object variable
Update:
I now see what you meant, I had previously assumed that menuItems already defined, but what you want to do is change the value of a key inside a nested object that is in this.state
This is something that React is not really built to do, you should keep your state relatively simple, and make separate React components for each menu item, then have them manage their own state. I would strongly recommend this approach because it will keep your code clean and robust. Don't be afraid to make more components!
However if you do want to keep all this nested state in one component (not advised), then you should first make a copy of the object you want to setState on.
var newMenuItems = _.clone(this.state.menuItems);
var iconText = (this.state.menuItems[category][index].bmIcon === "bookmark-o") ? "bookmark" : "bookmark-o";
newMenuItems[category][index].bmIcon = iconText;
this.setState({ menuItems: newMenuItems });
OR
var iconText = (this.state.menuItems[category][index].bmIcon === "bookmark-o") ? "bookmark" : "bookmark-o";
this.state.menuItems[category][index].bmIcon = iconText;
this.forceUpdate();
(First method preferred, but it requires you have something like underscore or lodash installed )
I have the data chat:
chat: {
id: 'ss3k5e6j1-6shhd6-sdasd3d3-23d5-gh67',
agentName: 'egaliciar',
agentAvatar: 'http://i.imgur.com/DY6gND0.png',
messages: [
{
id: 1,
lines: [
'Me pueden ayudar?',
'Tengo problemas con mis boletos',
'Hola buen dia...',
],
time: '17:20',
},
{
id: 2,
lines: ['¿Me podria regalar su nombres', 'Con gusto...'],
time: '17:22',
date: '23/ene/2012',
},
],
},
};
and when i do
const oldLines =Object.assign({}, this.state.chat);
oldLines.messages[0].lines.push('newValue');
My state Changed..... without this.setState({});
I Made a Clone;
var clone = JSON.parse(JSON.stringify(this.state.chat));
clone.messages[0].lines.push('new Value');
and the State maintain their state;
thus, the complete solution is for me:
var clone = JSON.parse(JSON.stringify(this.state.chat));
clone.messages[0].lines.push(questionAreaMessage); //the state maintains
this.setState({chat:clone}); //here the State change!!!!
So I'm displaying a observable array in my view, and I want to be able to remove an element from that list using asyncCommand. However, I'm not sure how I should be getting that element. Is there a way of accessing or passing the selected element into the asyncCommand method?
Thanks for the input
addGroupCmd = ko.asyncCommand({
execute: function (data, complete) {
//access your observable here with the data object
//EX. var demo = data.id();
},
canExecute: function (isExecuting) {
return !isExecuting && isEditing();
}
}),
Ok, so I figured it out with it little bit of google's help. All you have to do is pass in the data parameter and ko.lite will figure out what object your talking about. pretty nice, not really sure how it works, but it does.