I am tring to show todo list with load more option. I am appling limit.Limit is apply to list.But when i add loadmore()function. then i get error this.state.limit is null Wher i am wrong.Any one can suggest me.
here is my code
todoList.jsx
var TodoList=React.createClass({
render:function(){
var {todos}=this.props;
var limit = 5;
function onLoadMore() {
this.setState({
limit: this.state.limit + 5
});
}
var renderTodos=()=>{
return todos.slice(0,this.state.limit).map((todo)=>{
return(
<Todo key={todo.todo_id}{...todo} onToggle={this.props.onToggle}/>
);
});
};
return(
<div>
{renderTodos()}
<a href="#" onClick={this.onLoadMore}>Load</a>
</div>
)
}
});
module.exports=TodoList;
Changes:
1. First define the limit in state variable by using getInitialState method, you didn't define the limit, that's why this.state.limit is null.
2. Define all the functions outside of the render method.
3. Arrow function with renderTodos is not required.
4. Use this keyword to call the renderTodos method like this:
{this.renderTodos()}
Write it like this:
var TodoList=React.createClass({
getInitialState: function(){
return {
limit: 5
}
},
onLoadMore() {
this.setState({
limit: this.state.limit + 5
});
},
renderTodos: function(){
return todos.slice(0,this.state.limit).map((todo)=>{
return(
<Todo key={todo.todo_id}{...todo} onToggle={this.props.onToggle}/>
);
});
};
render:function(){
var {todos} = this.props;
return(
<div>
{this.renderTodos()}
<a href="#" onClick={this.onLoadMore}>Load</a>
</div>
)
}
});
This is witout button click.
As you all know react components has a function componentDidMount() which gets called automatically when the template of that component is rendered into the DOM. And I have used the same function to add the event listener for scroll into our div iScroll.
The scrollTop property of the element will find the scroll position and add it with the clientHeight property.
Next, the if condition will check the addition of these two properties is greater or equal to the scroll-bar height or not. If the condition is true the loadMoreItems function will run.
class Layout extends React.Component {
constructor(props) {
super(props);
this.state = {
items: 10,
loadingState: false
};
}
componentDidMount() {
this.refs.iScroll.addEventListener("scroll", () => {
if (this.refs.iScroll.scrollTop + this.refs.iScroll.clientHeight >=this.refs.iScroll.scrollHeight){
this.loadMoreItems();
}
});
}
displayItems() {
var items = [];
for (var i = 0; i < this.state.items; i++) {
items.push(<li key={i}>Item {i}</li>);
}
return items;
}
loadMoreItems() {
this.setState({ loadingState: true });
setTimeout(() => {
this.setState({ items: this.state.items + 10, loadingState: false });
}, 3000);
}
render() {
return (
<div ref="iScroll" style={{ height: "200px", overflow: "auto" }}>
<ul>
{this.displayItems()}
</ul>
{this.state.loadingState ? <p className="loading"> loading More Items..</p> : ""}
</div>
);
}
}
This is example
Related
I have created a simple React component with a table displaying 10 rows of data per page. The implementation of the pagination works as intended, but I want to be able to highlight the selected page.
In my constructor I have an initial state "active: null", which I then modify in a handleClick function.
constructor(props) {
super(props);
this.state = {
currentPage: 1,
eventsPerPage: 10,
active: null,
};
this.handleClick = this.handleClick.bind(this);
}
handleClick(index) {
this.setState({ currentPage: Number(index.target.id) });
if (this.state.active === index) {
this.setState({ active: null });
} else {
this.setState({ active: index });
}
}
And a function for setting the font-weight to bold.
myStyle(index) {
if (this.state.active === index) {
return 'bold';
}
return '';
}
Here is what I render.
const renderPageNumbers = pageNumbers.map((number, index) => (
<p
style={{ fontWeight: this.myStyle(index) }}
key={number}
id={number}
onClick={index => this.handleClick(index)}
>
{number}
</p>
));
return (
<div id="page-numbers">
{renderPageNumbers}
</div>
);
FYI: It's not the complete code.
I am not quite sure where I go wrong, any help is appreciated :)
pageNumbers.map((number, index) => index is zero based and am sure number starts from 1 so when index === 0 and number === 1, you would have this.myStyle(0) but
this.handleClick(0) will not work because you first #id === 1 not 0
why not just use number for your functions and remove index to safe confusion
You need to bind the context of the class to myStyle function in order to use this inside it.
So, in your constructor you should add it like this:
(see the last line)
constructor(props) {
super(props);
this.state = {
currentPage: 1,
eventsPerPage: 10,
active: null,
};
this.handleClick = this.handleClick.bind(this);
this.myStyle = this.myStyle.bind(this);
}
I've made this "Currency-Converter" to get an idea of how React works.
It works (more or less) but the result is shown with an offset:
You type "1" (Euro) => It shows "0 Dollar".
You type "10" => It shows "1.1308 Dollar".
You type "100" => It shows "11.308 Dollar".
...
var Display = React.createClass({
render: function() {
return (
<div>
<p>{this.props.euro + ' Euro are equal to ' + this.props.dollar + ' Dollar.'}</p>
</div>
)
}
});
var Converter = React.createClass({
getInitialState: function() {
return { euro: 0, dollar: 0, exchangeRate: 1.1308 }
},
convertEuroToDollar: function() {
this.setState({ euro: +document.querySelector('#amount-euro').value });
this.setState({ dollar: this.state.euro * this.state.exchangeRate });
},
render: function() {
return (
<div>
<input type="text" id="amount-euro" onKeyUp={this.convertEuroToDollar} />
<Display dollar={this.state.dollar} euro={this.state.euro} exchangeRate={this.state.exchangeRate} />
</div>
)
}
});
ReactDOM.render(
<Converter />,
document.querySelector('#app')
);
div {
margin: 30px 50px;
}
<div id="app"></div>
Live-Demo on CodePen: http://codepen.io/mizech/pen/vGbJxe
It should display the result (euro * exchangeRate) at once.
What I'm doing wrong here?
Calling two setStates one after all, you wasn't setting the euro state properly.
Being async, you was still using the old value of it.
From the docs:
setState() does not immediately mutate this.state but creates a
pending state transition. Accessing this.state after calling this
method can potentially return the existing value.
https://facebook.github.io/react/docs/component-api.html
To fix the problem, do:
convertEuroToDollar: function() {
const euro = +document.querySelector('#amount-euro').value
this.setState({
euro: euro,
dollar: euro * this.state.exchangeRate
});
},
Fixed example: http://codepen.io/FezVrasta/pen/xVeMMX
Second problem I see, it would be much better to use ref instead of document.querySelector.
convertEuroToDollar: function() {
const euro = +this.refs.amountEuro.value;
this.setState({
euro: euro,
dollar: euro * this.state.exchangeRate
});
},
render: function() {
return (
<div>
<input type="text" ref="amountEuro" onKeyUp={this.convertEuroToDollar} />
<Display dollar={this.state.dollar} euro={this.state.euro} exchangeRate={this.state.exchangeRate} />
</div>
)
}
I am working on a component where I need to display and hide a modal.
this is what I have in the render method in React
<div style={{visibility : this.state.displayModal}}>
<p>Pop up: Bet Behind Settings</p>
</div>
<button onClick={this._openModal}>CLICK</button>
and here is the function
_openModal = () => {
if (this.state.displayModal === 'hidden') {
this.setState({
displayModal : 'visible',
})
} else {
this.setState({
displayModal : 'hidden',
})
}
}
the main concern I have, is, how to set the state in a more elegant way, or this should be the way to do it ?
here the full code
constructor (props) {
super(props);
this.state = {
displayModal : 'hidden',
}
}
render () {
return (
<div style={{visibility : this.state.displayModal}}>
<p>Pop up: Bet Behind Settings</p>
</div>
<button onClick={this._openModal}>CLICK</button>
)
}
_openModal = () => {
if (this.state.displayModal === 'hidden') {
this.setState({
displayModal : 'visible',
})
} else {
this.setState({
displayModal : 'hidden',
})
}
}
so, what should be the way to this pop up in a React way.
I think it's a good way to do it. But it will be more concise if you make displayModel a boolean:
_toggleModal = () => this.setState({displayModal: !this.state.displayModal})
On a complex page using hidden will be a performance issue. Try something like this instead;
render() {
var returnIt;
if (this.state.hide) {
returnIt = null;
} else {
returnIt = (
<div style={{visibility : this.state.displayModal}}>
<p>Pop up: Bet Behind Settings</p>
</div>
<button onClick={this._openModal}>CLICK</button>
)
}
return (returnIt);
}
This is just a personal opinion, but I think a better UX would be that the button should only be used to open the modal; and the modal should be closed by either clicking the X in the modal (if there is) or when you click anywhere outside the modal.
That said if you definitely need the button to toggle between the 2 states, how about something like this?
constructor (props) {
super(props);
this.state = {
displayModal : false
}
}
render () {
return (
<div style={{visibility : this.state.displayModal === true ? 'visible' : 'hidden'}}>
<p>Pop up: Bet Behind Settings</p>
</div>
<button onClick={this._toggleModal}>CLICK</button>
)
}
_toggleModal = () => {
const current = this.state.displayModal;
this.setState({
displayModal : !current
});
}
Using https://github.com/fckt/react-layer-stack you can do like so:
import { Layer, LayerContext } from 'react-layer-stack'
// ... for each `object` in array of `objects`
const modalId = 'DeleteObjectConfirmation' + objects[rowIndex].id
return (
<Cell {...props}>
// the layer definition. The content will show up in the LayerStackMountPoint when `show(modalId)` be fired in LayerContext
<Layer use={[objects[rowIndex], rowIndex]} id={modalId}> {({
hideMe, // alias for `hide(modalId)`
index } // useful to know to set zIndex, for example
, e) => // access to the arguments (click event data in this example)
<Modal onClick={ hideMe } zIndex={(index + 1) * 1000}>
<ConfirmationDialog
title={ 'Delete' }
message={ "You're about to delete to " + '"' + objects[rowIndex].name + '"' }
confirmButton={ <Button type="primary">DELETE</Button> }
onConfirm={ this.handleDeleteObject.bind(this, objects[rowIndex].name, hideMe) } // hide after confirmation
close={ hideMe } />
</Modal> }
</Layer>
// this is the toggle for Layer with `id === modalId` can be defined everywhere in the components tree
<LayerContext id={ modalId }> {({showMe}) => // showMe is alias for `show(modalId)`
<div style={styles.iconOverlay} onClick={ (e) => showMe(e) }> // additional arguments can be passed (like event)
<Icon type="trash" />
</div> }
</LayerContext>
</Cell>)
// ...
I currently have this component in React.JS which shows all the Images passed to it in an array and onMouseOver it shows a button below. I planed on using setState to check the variable hover if is true or false and toggle the button of that image accordingly however I keep getting the following error:
Uncaught TypeError: Cannot read property 'state' of undefined
var ImageList = React.createClass({
getInitialState: function () {
return this.state = { hover: false };
},
getComponent: function(index){
console.log(index);
if (confirm('Are you sure you want to delete this image?')) {
// Save it!
} else {
// Do nothing!
}
},
mouseOver: function () {
this.setState({hover: true});
console.log(1);
},
mouseOut: function () {
this.setState({hover: false});
console.log(2);
},
render: function() {
var results = this.props.data,
that = this;
return (
<ul className="small-block-grid-2 large-block-grid-4">
{results.map(function(result) {
return(
<li key={result.id} onMouseOver={that.mouseOver} onMouseOut={that.mouseOut} ><img className="th" alt="Embedded Image" src={"data:" + result.type + ";" + "base64," + result.image} /> <button onClick={that.getComponent.bind(that, result.patientproblemimageid)} className={(this.state.hover) ? 'button round button-center btshow' : 'button round button-center bthide'}>Delete Image</button></li>
)
})}
</ul>
);
}
});
You get the error because you're storing the reference to this in a that variable which you're using to reference your event handlers, but you're NOT using it in the ternary expression to determine the className for the button element.
your code:
<button
onClick={ that.getComponent.bind(that, result.patientproblemimageid) }
className={ (this.state.hover) ? // this should be that
'button round button-center btshow' :
'button round button-center bthide'}>Delete Image
</button>
When you change this.state.hover to that.state.hover you won't get the error.
On a side note, instead of storing the reference to this in a that variable you can simple pass a context parameter to the map() method.
results.map(function (result) {
//
}, this);
In ES5 format you cannot set this.state directly
var ImageList = React.createClass({
getInitialState: function () {
return { hover: false };
},
render : function(){
return(<p>...</p>);
});
However with new ES6 syntax you can essentially manage this:
class ImageList extends React.Component{
constructor (props) {
super(props);
this.state = {hover : false};
}
render (){ ... }
}
I've just started learning React and have a question.
I want to do the following:
If a user clicks on a paragraph I want to change the element to an input field that has the contents of the paragraph prefilled.
(The end goal is direct editing if the user has certain privileges)
I'm come this far but am totally at a loss.
var AppHeader = React.createClass({
editSlogan : function(){
return (
<input type="text" value={this.props.slogan} onChange={this.saveEdit}/>
)
},
saveEdit : function(){
// ajax to server
},
render: function(){
return (
<header>
<div className="container-fluid">
<div className="row">
<div className="col-md-12">
<h1>{this.props.name}</h1>
<p onClick={this.editSlogan}>{this.props.slogan}</p>
</div>
</div>
</div>
</header>
);
}
});
How can I override the render from the editSlogan function?
If I understand your questions correctly, you want to render a different element in case of an "onClick" event.
This is a great use case for react states.
Take the following example
React.createClass({
getInitialState : function() {
return { showMe : false };
},
onClick : function() {
this.setState({ showMe : true} );
},
render : function() {
if(this.state.showMe) {
return (<div> one div </div>);
} else {
return (<a onClick={this.onClick}> press me </a>);
}
}
})
This will change the components state, and makes React render the div instead of the a-tag. When a components state is altered(using the setState method), React calculates if it needs to rerender itself, and in that case, which parts of the component it needs to rerender.
More about states
https://facebook.github.io/react/docs/interactivity-and-dynamic-uis.html
You can solve it a little bit more clear way:
class EditableLabel extends React.Component {
constructor(props) {
super(props);
this.state = {
text: props.value,
editing: false
};
this.initEditor();
this.edit = this.edit.bind(this);
this.save = this.save.bind(this);
}
initEditor() {
this.editor = <input type="text" defaultValue={this.state.text} onKeyPress={(event) => {
const key = event.which || event.keyCode;
if (key === 13) { //enter key
this.save(event.target.value)
}
}} autoFocus={true}/>;
}
edit() {
this.setState({
text: this.state.text,
editing: true
})
};
save(value) {
this.setState({
text: value,
editing: false
})
};
componentDidUpdate() {
this.initEditor();
}
render() {
return this.state.editing ?
this.editor
: <p onClick={this.edit}>{this.state.text}</p>
}
}
//and use it like <EditableLabel value={"any external value"}/>;