I'm new to javascript and its ecosystem. I'm trying to build some components using mithril.js. My goal is to have a component that shows some properties and provides a couple of button for each of them. Just to learn about mithril.js and jsx. Here is what I did so far:
const m = require("mithril");
var Something = {
_increase: function(category) {
console.log("increase category: "+category);
},
_decrease: function(category) {
console.log("decrease category: "+category);
},
view: function(vnode) {
return <div>
{Object.keys(vnode.attrs.categories).map((category)=> {
return <div>
<label for={category}>{category}</label>
<input type="number" id={category} value={vnode.attrs.categories[category]} />
<button type="button" onclick="{this._increase(category)}">MORE</button>
<button type="button" onclick="{this._decrease(category)}">LESS</button>
</div>
})}
</div>
}
}
export default Something;
Well, component seems to work fine, node doesn't complain and labels and buttons and fields are displayed on page, but, when I click on a button, nothing happen. It looks like event isn't fired. What's wrong?
Two things: (1) I think you should just put the function into the onclick handler braces instead of encoding the function in a string. (2) It looks like you're immediately invoking the function, not declaring that the onclick handler is a function that uses the category argument. Try passing in an anonymous function with no arguments, that way you when the onclick event is fired it can take in the category as a parameter:
onclick={() => this._increase(category)}
onclick={() => this._decrease(category)}
Related
I'm wondering what I am doing wrong here, from what I can see this is the solution: Vue: method is not a function within inline-template component tag
However the method is still not triggering.
<b-table
:items="filtered"
:fields="fields"
sort-icon-left
responsive="sm"
#card-click="setUpdate"
>
<template v-slot:head()="data">
<span class="text-info">{{ data.label.toUpperCase() }}</span>
<button #click="$emit('card-click', data)">filter</button>
<input
v-show="data.field.showFilters"
v-model="filters[data.field.key]"
:placeholder="data.label"
/>
</template>
</b-table>
methods: {
setUpdate(field) {
console.log("hello");
console.log(field);
this._originalField = Object.assign({}, field);
field.showFilters = true;
}
}
Update
So the #click allowed me to to trigger the event but this lead to the table wouldn't update with the changed data with showFilters. Thanks to MattBoothDev I found event-based-refreshing-of-data, however this oddly now prevents the data from changing. I.e. if field.showFilters is true it's true if I click the button.
methods: {
setUpdate(field) {
this._originalField = Object.assign({}, field);
field.showFilters = !field.showFilters;
this.refreshTable();
console.log(field.showFilters);
},
refreshTable() {
this.$root.$emit("bv::refresh::table", "my-table");
}
}
It looks like you're using Bootstrap Vue?
What you're essentially doing here is putting a listener on the <b-table> tag for card-click but that event is essentially not happening within a child component of <b-table>.
Regardless, I'm not even sure you need the event.
<button #click="$emit('card-click', data)">filter</button>
can easily just be
<button #click="setUpdate(data)">filter</button>
EDIT:
It is good practice to use MVVM for Vue.js as well.
Rather than: #click="$emit('card-click', data)"
Should be: #click="onFilterClicked"
Then:
methods: {
onFilterClicked (data) {
this.$emit('an-event', data.some.property)
}
}
This will make testing your code a lot easier.
The buttons i create using below seems to lag in the selectedButtonIdx value.
Is the toggleSelected not complete by the time getClass is called ?
function ButtonGroup(props) {
const [selectedButtonIdx,setIdx]=useState(props.loadCurrentAsIndex);
const toggleSelected = (e) => {
setIdx(parseInt(e.target.dataset.index));
props.onclick(e);
};
const getClass = (index) => {
return (selectedButtonIdx === index) ? classnames('current', props.btnClass)
: classnames(props.btnClass)
};
let buttons = props.buttons.map((b, idx) => <Button key={idx} value={b.value} index={idx} text={b.text}
onclick={e => toggleSelected(e)}
btnClass={getClass(idx)}/>);
return (
<div>
{buttons}
</div>
);
}
Every onclick is expected to show the user which button in the group was clicked by changing its class.
By looking at this,
<Button
key={idx}
value={b.value}
index={idx}
text={b.text}
onclick={e => toggleSelected(e)}
btnClass={getClass(idx)}
/>
Button is your custom component,
Two things to notice here,
You have provided onclick (c is small) props, in you actual component it should be onClick={props.onclick}
You have used e.target.dataset.index, to work with dataset we should have attribute with data- prefix. So your index should be data-index in your actual component.
So finally your Button component should be,
const Button = (props) => {
return <button text={props.text} data-index={props.index} onClick={props.onclick} className={props.btnClass}>{props.value}</button>
}
Demo
The function setIdx, returned from useState is asynchronous, this means that it may be not be finished by the time you run your next function (as you guessed).
Take a look at useEffect it allows you to specify a function to run once an item in your state changes, this method will ensure your functions are called in the right order.
By now I don't see anything wrong here.
How it works:
initial render happens, onClick event listener is bound
user clicks a button, event handler calls setIdx triggering new render
new render is initiated, brand new selectedButtonIdx is used for rendering(and for getClass call as well)
See, there is no reason to worry about if setIdx is sync function or async.
I am trying to create a custom event in one component and add an event listener in another component. The component that is listening for the event contains a function that I want to execute on the event. Below are what I have in the two components, I just feel like I'm going about this in the wrong way...
Component #1
toggleWidget() {
const event = new CustomEvent('sliderClicked', {
bubbles: true,
});
const sliderToggle = document.getElementById('input');
sliderToggle.dispatchEvent(event);
this.setState({
checked: !this.state.checked,
});
}
/* and then in my render... */
render() {
const displaySlider = this.state.isSliderDisplayed ? (
<div className="slider-container" >
<label className="switch" htmlFor="input">
<input type="checkbox" checked={this.state.checked} onChange={this.toggleWidget} id="input" />
<span className="slider round" />
</label>
<p className="batch-slider-title"> Batch Widget </p>
</div>) : null;`
Component Two
window.addEventListener('sliderClicked', this.refreshLayout);`
Any ideas as to what I may be doing wrong?
Basically it should work, but in react - if you rendered an element in a component you can use the ref to access it:
<input
type="checkbox"
checked={this.state.checked}
onChange={this.toggleWidget}
id="input"
ref={(c) => this.input = c}
/>
And your toggleWidget function should be something like this:
toggleWidget() {
...
this.input.dispatchEvent(event);
...
}
In React it's pretty common to pass down callbacks from parent to child.
const Child = ({handleClick}) => (
<div onClick={ handleClick } >Click me!</div>
);
const Parent = () => {
const childClickHandler = event => {
// do stuff
alert('My child is calling?');
}
return (
<Child handleClick={ childClickHandler }/>
);
};
Maybe that could work for you? You can try the code here. (JSFiddle)
Refs are generally considered something to avoid in React as they couple components together. see the documentation here:
https://facebook.github.io/react/docs/refs-and-the-dom.html
Your first inclination may be to use refs to "make things happen" in your app. If this is the case, take a moment and think more critically about where state should be owned in the component hierarchy. Often, it becomes clear that the proper place to "own" that state is at a higher level in the hierarchy. See the Lifting State Up guide for examples of this.
Try using a global state container like redux and when you "toggleWidget" in one component, set a property in your redux store. Listen to that property by setting it as a prop in your second component(the one that you want to respond to a change/toggle). On change of that property your component will have the "componentWillReceiveProps" lifecycle method called and you can then have your "responding" component take whatever action you like.
I have an html template that i'm using template literals for. The function looks like the below
// postCreator.js
export const blogPostMaker = ({ title, content, address, id }, deletePost) => {
const innerHtml = `
<blog-post>
<h1 class='title'>${title}</h1>
<p class='content'>${content}</p>
<p class='address'>${address}</p>
<button onclick='${() => deletePost(id)}'>Delete</button>
</blog-post>
`
return innerHtml
}
//Blog.js
postHelper.getSeriesOfPosts(10)
.then(resp => {
resp.forEach(post => (blogDiv.innerHTML += blogPostMaker(post, postHelper.deletePost)))
})
What I can't figure out is how to get the onclick to work. I've tried passing in an anon function in Blog.js to the postCreator as well with no luck.
Any ideas?
If you don't want to expose the event callback globally, you should attach it in the JS part of the code with addEventListener() :
// postCreator.js
export const blogPostMaker = ({ title, content, address, id }) =>
`
<blog-post id='${id}'>
<h1 class='title'>${title}</h1>
<p class='content'>${content}</p>
<p class='address'>${address}</p>
<button>Delete</button>
</blog-post>
`
//Blog.js
postHelper.getSeriesOfPosts(10).then(resp => {
resp.forEach(post => {
blogDiv.innerHTML += blogPostMaker(post)
blogDiv.querySelector(`blog-post[id="${post.id}"] > button`)
.addEventListener('click', () => postHelper.deletePost(post.id))
})
Note: it's not the most efficient way to do it but it keeps your file structure.
Instead I would create the <button> directly with createElement() and then add it to DOM with appendChild(), or I would use a DocumentFragment or a <template> in order to avoid querySelector() on all of the blogDiv.
If you absolutely want to use inline JS without exposing the helper you'll need to define your as a component (for example a Custom Element).
Miroslav Savovski's solution works but they did not explain why, so I thought I would add this answer with the reasoning behind that and a step-by-step of how it is actually working, and why the OP's solution was not working initially.
TLDR? Scroll to the last two code snippets.
With template literals when you put a function inside of them it executes that function, so let's say we have a simple function like this that just returns a string of 'blue':
const getBlueColor = () => 'blue'
And then we call this function inside of a template literal like this:
<div>${getBlueColor()}</div>
What happens is that the getBlueColor() is called right when that code is executed.
Now lets say we wanted to do this onclick instead like this:
<div onclick="${getBlueColor()}"></div>
What is happening here is that getBlueColor is not executed onclick, it's actually executed whenever this template literal is executed.
The way we fix this is to prevent the template literal from executing this function by simply removing the template literal:
<div onclick="getBlueColor()"></div>
But now let's say you want to pass in some parameters to a function like getOppositeColor(color) like this:
<div onclick="getOppositeColor(color)"><div>
This will not work because color won't be defined. So you need to wrap that with a template literal and in a string like this:
<div onclick="getOppositeColor('${color}')"><div>
Now with this you will be calling the onclick when the user clicks the button, and you will be passing it a string of the color like this:
getOppositeColor('blue')
const markUp = `
<button onclick="myFunction()">Click me</button>
`;
document.body.innerHTML = markUp;
window.myFunction = () => {
console.log('Button clicked');
};
Consider this example:
var Field = React.createClass({
render: function () {
// never renders new value...
return (
<div>
<input type="text" defaultValue={this.props.value || ''} />
</div>
);
}
});
var App = React.createClass({
getInitialState: function () {
return {value: 'Hello!'};
},
changeTo: function (str) {
this.setState({value: str});
},
render: function () {
return (
<div>
<Field value={this.state.value} />
<button onClick={this.changeTo.bind(null, 'Whyyyy?')}>Change to "Whyyyy?"</button>
<button onClick={this.changeTo.bind(null, void 0)}>Change to undefined</button>
</div>
);
}
});
React.render(
<App />,
document.getElementById('app')
);
I want to pass value into defaultValue as prop of dumb input component. However it never re-renders it.
As a previous answer mentioned, defaultValue only gets set on initial load for a form. After that, it won't get "naturally" updated because the intent was only to set an initial default value.
You can get around this if you need to by passing a key to the wrapper component, like on your Field or App component, though in more practical circumstances, it would probably be a form component. A good key would be a unique value for the resource being passed to the form - like the id stored in the database, for example.
In your simplified case, you could do this in your Field render:
<div key={this.props.value}>
<input type="text" defaultValue={this.props.value || ''} />
</div>
In a more complex form case, something like this might get what you want if for example, your onSubmit action submitted to an API but stayed on the same page:
const Form = ({item, onSubmit}) => {
return (
<form onSubmit={onSubmit} key={item.id}>
<label>
First Name
<input type="text" name="firstName" defaultValue={item.firstName} />
</label>
<label>
Last Name
<input type="text" name="lastName" defaultValue={item.lastName} />
</label>
<button>Submit!</button>
</form>
)
}
Form.defaultProps = {
item: {}
}
Form.propTypes = {
item: PropTypes.object,
onSubmit: PropTypes.func.isRequired
}
When using uncontrolled form inputs, we generally don't care about the values until after they are submitted, so that's why it's more ideal to only force a re-render when you really want to update the defaultValues (after submit, not on every change of the individual input).
If you're also editing the same form and fear the API response could come back with different values, you could provide a combined key of something like id plus timestamp.
defaultValue only works for the initial load. After that, it won't get updated. You need to maintain the state for you Field component:
var Field = React.createClass({
//transfer props to state on load
getInitialState: function () {
return {value: this.props.value};
},
//if the parent component updates the prop, force re-render
componentWillReceiveProps: function(nextProps) {
this.setState({value: nextProps.value});
},
//re-render when input changes
_handleChange: function (e){
this.setState({value: e.target.value});
},
render: function () {
// render based on state
return (
<div>
<input type="text" onChange={this._handleChange}
value={this.state.value || ''} />
</div>
);
}
});
I'm fairly certain this has to do with Controlled vs. Uncontrolled inputs.
If I understand correctly, since your <input> is Uncontrolled (doesn't define a value attribute), then the value will always resolve to the value that it is initialized with. In this case Hello!.
In order to overcome this issue, you can add a value attribute and set it during the onChange:
var Field = React.createClass({
render: function () {
// never renders new value...
return (
<div>
<input type="text" defaultValue={this.props.default || ''} value={this.props.value} />
</div>
);
}
});
Here is a plunker showing the change.
You can make the input conditionally and then every time you want to force an update of the defaultValue you just need to unmount the input and then immediately render it again.
The issue is here:
onClick={this.changeTo.bind(null, 'Whyyyy?')}
I'm curious why you bind to null.
You want to bind to 'this', so that changeTo will setState in THIS object.
Try this
<button onClick={this.changeTo.bind(this, 'Whyyyy?')}>Change to "Whyyyy?"</button>
<button onClick={this.changeTo.bind(this, void 0)}>Change to undefined</button>
In Javascript, when a function is called, its called in the scope where it was called from, not where it was written (I know, seems counter intuitive). To ensure it is called in the context you write it, you need to '.bind(this)'.
To learn more about binding and function scope, there are lots of online tutes, (some much better than others) - you might like this one: http://ryanmorr.com/understanding-scope-and-context-in-javascript/
I also recommend using the React Dev tools if you are using firefox or chrome, this way you would have been able to see that state.message was not changing:
https://facebook.github.io/react/blog/2015/09/02/new-react-developer-tools.html
Use conditional rendering, then the component will load correct initial value. Something like in this module:
class MenuHeaderInput extends React.Component{
constructor(props){
super(props);
this.handleBlur = this.handleBlur.bind (this);
}
handleBlur (e) {
this.props.menuHeaderUpdate(e.target.value);
}
render(){
if (this.props.menuHeader) {
return (
<div className="w3-row w3-margin" onClick = {() => this.props.handleTitleClick (10)}>
<div className="w3-third" ><pre></pre></div>
<input
className = {"w3-third w3-input w3-jumbo " + EDIT_COLOR}
type = "text"
defaultValue = {this.props.menuHeader}
onBlur = {this.handleBlur}
/>
<div className="w3-third" ><pre></pre></div>
</div>
)
}
else {
return null;
}
}
}
Related to Sia's excellent answer above: https://stackoverflow.com/a/41962233/4142459.
For my case I had a few ways in which a form could be updated:
users could input values into form fields
An API request allowed users to restore from previous versions
Users could navigate to a filled out form (using queryParams of the URL)
clearing the form fields.
Etc more ways of allowing all the fields or just a single change to happen from user action or websockets.
I found that the easiest way to make sure the state of the form is reflected in its inputs is indeed:
To provide a manually-controlled key prop on the top level of the form or parent element to the form (as long as it is above the inputs in the DOM tree.
When users are typing a key update does not need to happen.
I made the key be a simple formHistoricalVersion and as certain updates external to a user typing/selecting/etc interacting with the form field's values happened I incremented the formHistoricalVersion.
This made sure that the state of the form whether by user action or by API request was in-sync--I had complete control over it.
Other solutions I tried:
While making the API request make the whole form disappear (when loading change to a loading spinner instead of the form). Disadvantage to performance and for clearForm it was a bit crazy to do, but possible with setImmediate to convert the form to a loading spinner when they first clear it, then setting isLoading back to false in the setImmediate.
Adding a key on each input: this worked amazingly, but it had a weird blip whenever users would type so I had to get rid of it.
Putting a static key for the form (field.id) (as suggested by above answer) didn't cover all the use cases I had.
In conclusion, it worked pretty easily to set the key of the form with react/redux, I just would add the equivalent of:
return {
...state,
formFieldState: payload.formFields,
historicalFormVersion: state.historicalFormVersion + 1
}
This was necessary because I was using some 3rd party libraries and my own Numeric Input that took in value as a prop but used value as a defaultValue:
const NumberDisplay: FunctionComponent = ({ value, setValue }) => (
<input
defaultValue={convertToSpecialNumberDisplay(value)}
onBlur={(e) => convertToSpecialNumberDisplay(e.target.value)}
onFocus={(e) => convertToNumberFromDisplay(e.target.value)}
onChange={(e) => setValue(e.target.value)}
/>
)
Approximate Redux of overall Form:
const FullForm: FunctionComponent = () => {
const dispatch = useDispatch();
const formState = useState((state) => state.formState);
const formHistoricalVersion = useState((state) => state.formHistoricalVersion);
return (
<form key={formHistoricalVersion}>
{renderFormFields(formState, dispatch)}
</form>
)
}
I also face this problem, what I did was to manually update the input value when the props has change. Add this to your Field react class:
componentWillReceiveProps(nextProps){
if(nextProps.value != this.props.value) {
document.getElementById(<element_id>).value = nextProps.value
}
}
You just need to add an id attribute to your element so that it can be located.