Develop Reference

setState updates state and triggers render but I still don't see it in view

I have a simple word/definition app in React. There is an edit box that pops up to change definition when a user clicks on "edit". The new definition provided is updated in the state when I call getGlossary(), I see the new definition in inspector and a console.log statement in my App render() function triggers too. Unfortunately, I still have to refresh the page in order for the new definition to be seen on screen. I would think that calling set state for this.state.glossary in the App would trigger a re-render down to GlossaryList and then to GlossaryItem to update it's definition but I'm not seeing it :(.
App.js
class App extends React.Component {
constructor() {
super();
this.state = {
glossary: [],
searchTerm: '',
}
this.getGlossary = this.getGlossary.bind(this); //not really necessary?
this.handleSearchChange = this.handleSearchChange.bind(this);
this.handleAddGlossaryItem = this.handleAddGlossaryItem.bind(this);
this.handleDeleteGlossaryItem = this.handleDeleteGlossaryItem.bind(this);
//this.handleUpdateGlossaryDefinition = this.handleUpdateGlossaryDefinition.bind(this);
}
getGlossary = () => {
console.log('getGlossary fired');
axios.get('/words').then((response) => {
const glossary = response.data;
console.log('1: ' + JSON.stringify(this.state.glossary));
this.setState({ glossary }, () => {
console.log('2: ' + JSON.stringify(this.state.glossary));
});
})
}
componentDidMount = () => {
//console.log('mounted')
this.getGlossary();
}
handleSearchChange = (searchTerm) => {
this.setState({ searchTerm });
}
handleAddGlossaryItem = (glossaryItemToAdd) => {
//console.log(glossaryItemToAdd);
axios.post('/words', glossaryItemToAdd).then(() => {
this.getGlossary();
});
}
handleDeleteGlossaryItem = (glossaryItemId) => {
console.log('id to delete: ' + glossaryItemId);
axios.delete('/words', {
data: { glossaryItemId },
}).then(() => {
this.getGlossary();
});
}
render() {
console.log('render app fired');
const filteredGlossary = this.state.glossary.filter((glossaryItem) => {
return glossaryItem.word.toLowerCase().includes(this.state.searchTerm.toLowerCase());
});
return (
<div>
<div className="main-grid-layout">
<div className="form-left">
<SearchBox handleSearchChange={this.handleSearchChange} />
<AddWord handleAddGlossaryItem={this.handleAddGlossaryItem} />
</div>
<GlossaryList
glossary={filteredGlossary}
handleDeleteGlossaryItem={this.handleDeleteGlossaryItem}
getGlossary={this.getGlossary}
//handleUpdateGlossaryDefinition={this.handleUpdateGlossaryDefinition}
/>
</div>
</div>
);
}
}
export default App;
GlossaryItem.jsx
import React from 'react';
import EditWord from './EditWord.jsx';
const axios = require('axios');
class GlossaryItem extends React.Component {
constructor(props) {
super(props);
this.state = {
isInEditMode: false,
}
this.glossaryItem = this.props.glossaryItem;
this.handleDeleteGlossaryItem = this.props.handleDeleteGlossaryItem;
this.handleUpdateGlossaryDefinition = this.handleUpdateGlossaryDefinition.bind(this);
this.handleEditClick = this.handleEditClick.bind(this);
}
handleUpdateGlossaryDefinition = (updateObj) => {
console.log('update object: ' + JSON.stringify(updateObj));
axios.put('/words', {
data: updateObj,
}).then(() => {
this.props.getGlossary();
}).then(() => {
this.setState({ isInEditMode: !this.state.isInEditMode });
//window.location.reload();
});
}
handleEditClick = () => {
// display edit fields
this.setState({ isInEditMode: !this.state.isInEditMode });
// pass const name = new type(arguments); data up to App to handle with db
}
render() {
return (
<div className="glossary-wrapper">
<div className="glossary-item">
<p>{this.glossaryItem.word}</p>
<p>{this.glossaryItem.definition}</p>
<a onClick={this.handleEditClick}>{!this.state.isInEditMode ? 'edit' : 'cancel'}</a>
<a onClick={() => this.handleDeleteGlossaryItem(this.glossaryItem._id)}>delete</a>
</div>
{this.state.isInEditMode ?
<EditWord
id={this.glossaryItem._id}
handleUpdateGlossaryDefinition={this.handleUpdateGlossaryDefinition}
/> : null}
</div>
);
}
}
EditWord
import React from 'react';
class EditWord extends React.Component {
constructor(props) {
super(props);
this.state = {
definition: ''
};
this.handleUpdateGlossaryDefinition = this.props.handleUpdateGlossaryDefinition;
this.handleChange = this.handleChange.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}
handleChange(event) {
let definition = event.target.value;
this.setState({ definition });
}
handleSubmit(event) {
//console.log(event.target[0].value);
let definition = event.target[0].value;
let update = {
'id': this.props.id,
'definition': definition,
}
//console.log(update);
this.handleUpdateGlossaryDefinition(update);
event.preventDefault();
}
render() {
return (
<form onSubmit={this.handleSubmit} className="glossary-item">
<div></div>
<input type="text" name="definition" placeholder='New definition' value={this.state.definition} onChange={this.handleChange} />
<input type="submit" name="update" value="Update" />
</form>
);
}
}
export default EditWord;
Thank you

One possible way I can see to fix this is to map the data to make the id uniquely identify each list item (even in case of update). We can to do this in getGlossary() by modifying the _id to _id + definition.
getGlossary = () => {
console.log('getGlossary fired');
axios.get('/words').then((response) => {
// Map glossary to uniquely identify each list item
const glossary = response.data.map(d => {
return {
...d,
_id: d._id + d.definition,
}
});
console.log('1: ' + JSON.stringify(this.state.glossary));
this.setState({ glossary }, () => {
console.log('2: ' + JSON.stringify(this.state.glossary));
});
})
}

In the constructor of GlossaryItem I set
this.glossaryItem = this.props.glossaryItem;
because I am lazy and didn't want to have to write the word 'props' in the component. Turns out this made react loose reference somehow.
If I just remove this line of code and change all references to this.glossaryItem.xxx to this.pros.glossaryItem.xxx then it works as I expect! On another note, the line of code can be moved into the render function (instead of the constructor) and that works too, but have to make sure I'm accessing variables properly in the other functions outside render.

HandleClick not changing the state

I have the below where it should display images of beers retrieved from an API. Each image has a handleClick event which will direct them to a details page about this beer. My code below doesn't render the beers at all and goes straight to the details page of a random beer. Can anyone help me figure out why?
Thanks
export default class GetBeers extends React.Component {
constructor() {
super();
this.state = {
beers: [],
showMethod: false,
beerDetails: []
};
this.getBeerInfo = this.getBeerInfo.bind(this);
this.handleClick = this.handleClick.bind(this);
}
handleClick(details) {
this.setState({
showMethod: !this.state.showMethod,
beerDetails: details
});
}
render() {
if(this.state.showMethod) {
return (
<Beer details = {this.state.beerDetails}/>
);
}
else {
return (
<div>{this.state.beers.map(each=> {
return <img className = "img-beer" onClick = {this.handleClick(each)} src={each.image_url}/>
})}</div>
);
}
}
componentDidMount() {
this.getBeerInfo()
}
getBeerInfo() {
...gets info
}
}

When you use onClick like that you run the function at the render.
So you have to use arrow function:
Not Working:
<img className = "img-beer" onClick = {this.handleClick(each)} src={each.image_url}/>
Working:
<img className = "img-beer" onClick = {() => this.handleClick(each)} src={each.image_url}/>

The main issue is not calling the handle properly.
Also, I noticed that you are binding the functions in the constructor. It might be simpler to use ES6 function creation, so the scope of the class is bound to your handle method.
export default class GetBeers extends React.Component {
constructor() {
super();
this.state = {
beers: [],
showMethod: false,
beerDetails: []
};
}
handleClick = (details) => {
this.setState({
showMethod: !this.state.showMethod,
beerDetails: details
});
}
render() {
if(this.state.showMethod) {
return (
<Beer details = {this.state.beerDetails}/>
);
}
else {
return (
<div>{this.state.beers.map(each=> {
return <img className = "img-beer" onClick = {() => this.handleClick(each)} src={each.image_url}/>
})}</div>
);
}
}
componentDidMount() {
this.getBeerInfo()
}
getBeerInfo = () => {
...gets info
}
}

React Expected an assignment or function call and instead saw an expression

I'm trying to render the data from my database get this instead Failed to compile.
./src/components/list-pets.component.js
Line 38:5: Expected an assignment or function call and instead saw an expression no-unused-expressions
Search for the keywords to learn more about each error.enter code here
Here is my code from the trouble component
import React, { Component } from 'react';
import axios from 'axios';
export default class ListPets extends Component {
constructor(props) {
super(props);
this.state = {
pets: []
};
}
componentDidMount = () => {
this.getPets();
};
getPets = () => {
axios.get('http://localhost:5000/pets')
.then((response) => {
const data = response.data;
this.setState({ pets: data });
console.log('Data has been received!');
})
.catch((err) => {
console.log(err);
});
}
displayPet = (pets) => {
if (!pets.length) return null;
return pets.map((pet, index) => {
<div key={index}>
<h3>{pet.name}</h3>
<p>{pet.species}</p>
</div>
});
};
render() {
console.log('State: ', this.state);
return (
<div className='adopt'>
{this.displayPet(this.state.pets)}
</div>
)
}
}

You need to return a value at each pets.map iteration, currently you’re returning undefined.
return pets.map((pet, index) => {
return (
<div key={index}>
<h3>{pet.name}</h3>
<p>{pet.species}</p>
</div>
)
});

You have to wait until fetching data is completed.
You should have to define the loading bar while fetching.
class App extends Component {
constructor() {
super();
this.state = {
pageData: {},
loading: true
}
this.getData();
}
async getData(){
const res = await fetch('/pageData.json');
const data = await res.json();
return this.setState({
pageData: data,
loading: false
});
}
componentDidMount() {
this.getData();
}
render() {
const { loading, pageData } = this.state;
if (loading){
return <LoadingBar />
}
return (
<div className="App">
<Navbar />
</div>
);
}
}

Why is this undefined within reactjs component method

I have a simple search bar which uses a react-autosuggest. When I create a suggestion, I want to attach an onClick handler. This onClick has been passed down from a parent class. When the suggestion is rendered however, this is undefined and therefore the click handler is not attached.
I have attached the component below, the logic which is not working is in the renderSuggestion method.
import Autosuggest from 'react-autosuggest'
import React from 'react'
export class SearchBar extends React.Component {
static getSuggestionValue(suggestion) {
return suggestion;
}
static escapeRegexCharacters(str) {
return str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
}
constructor(props) {
super(props);
this.state = {
value: '',
suggestions: [],
listOfValues: this.props.tickers
};
}
onChange = (event, { newValue, method }) => {
this.setState({
value: newValue
});
};
onSuggestionsFetchRequested = ({ value }) => {
this.setState({
suggestions: this.getSuggestions(value)
});
};
onSuggestionsClearRequested = () => {
this.setState({
suggestions: []
});
};
renderSuggestion(suggestion) {
return (
<span onClick={() => this.props.clickHandler(suggestion)}>{suggestion}</span>
);
}
getSuggestions(value) {
const escapedValue = SearchBar.escapeRegexCharacters(value.trim());
if (escapedValue === '') {
return [];
}
const regex = new RegExp('^' + escapedValue, 'i');
return this.state.listOfValues.filter(ticker => regex.test(ticker));
}
render() {
const { value, suggestions } = this.state;
const inputProps = {
placeholder: "Search for stocks...",
value,
onChange: this.onChange
};
return (
<Autosuggest
suggestions={suggestions}
onSuggestionsFetchRequested={this.onSuggestionsFetchRequested}
onSuggestionsClearRequested={this.onSuggestionsClearRequested}
getSuggestionValue={SearchBar.getSuggestionValue}
renderSuggestion={this.renderSuggestion}
inputProps={inputProps} />
);
}
}

This is becuase you need to bind "this" to your function.
If you add this code to your constructor
constructor(props) {
super(props);
this.state = {
value: '',
suggestions: [],
listOfValues: this.props.tickers
};
//this line of code binds this to your function so you can use it
this.renderSuggestion = this.renderSuggestion.bind(this);
}
It should work. More info can be found at https://reactjs.org/docs/handling-events.html

In the scope of renderSuggestion, this isn't referring to the instance of the class.
Turning renderSuggestion into an arrow function like you've done elsewhere will ensure that this refers to the instance of the class.
renderSuggestion = (suggestion) => {
return (
<span onClick={() => this.props.clickHandler(suggestion)}>{suggestion}</span>
);
}

ES6 - Warning: setState(…): Cannot update during an existing state transition

I am rewriting some old ReactJS code, and got stuck fixing this error (the error repeats about 1700 times in the console, the DOM does not render at all):
Warning: setState(...): Cannot update during an existing state
transition (such as within render or another component's
constructor). Render methods should be a pure function of props and
state; constructor side-effects are an anti-pattern, but can be moved
to componentWillMount.
I am a Component that passes it's state down to a component that should render some controls. Based on the clicked controls, the state should change, and new controls should render.
So this is my Container component:
class TeaTimer extends Component {
constructor(props) {
super(props);
this.state = {
count: 120,
countdownStatus: 'started'
}
}
componentDidUpdate(prevProps, prevState) {
if (this.state.countdownStatus !== prevState.countdownStatus) {
switch (this.state.countdownStatus) {
case 'started':
this.startTimer();
break;
case 'stopped':
this.setState({count:0});
}
}
}
componentWillUnmount() {
clearInterval(this.timer);
delete this.timer;
}
startTimer() {
this.timer = setInterval(() => {
let newCount = this.state.count -1;
this.setState({
count: newCount >= 0 ? newCount : 0
});
if(newCount === 0) {
this.setState({countdownStatus: 'stopped'});
}
}, 1000)
}
handleStatusChange(newStatus) {
this.setState({ countdownStatus: newStatus });
}
render() {
let {count, countdownStatus} = this.state;
let renderStartStop = () => {
if (countdownStatus !== 'stopped') {
return <StartStop countdownStatus={countdownStatus} onStatusChange={this.handleStatusChange()}/>
} else {
return <div>This will be the slider form</div>
}
};
return(
<div className={styles.container}>
<p>This is the TeaTimer component</p>
<Clock totalSeconds={count}/>
{renderStartStop()}
</div>
)
}
}
And this is my controls component:
class StartStop extends Component {
constructor(props) {
super(props);
}
onStatusChange(newStatus) {
return() => {
this.props.onStatusChange(newStatus);
}
}
render() {
let {countdownStatus} = this.props;
let renderStartStopButton = () => {
if(countdownStatus === 'started') {
return <button onClick={()=> this.onStatusChange('stopped')}>Reset</button>;
} else {
return <button onClick={()=> this.onStatusChange('started')}>Start</button>
}
};
return(
<div className={styles.tt.Controls}>
{renderStartStopButton()}
</div>
)
}
}
StartStop.propTypes = {
countdownStatus: React.PropTypes.string.isRequired,
onStatusChange: React.PropTypes.func.isRequired
};
I am sorry about the wall of text, but I really can;t figure out where the error is coming from - and therefor don't know which part of the code I can leave out.
I have tried implementing the solution found in a seemingly related question, but can't get it to work either.

I think you have a typo in this line:
return <StartStop countdownStatus={countdownStatus} onStatusChange={this.handleStatusChange()}/>
It should be:
return <StartStop countdownStatus={countdownStatus} onStatusChange={() => this.handleStatusChange}/>
You seem to be calling the method handleStatusChange instead of passing it as a callback.

Your metods call each other so you must define two instance of your metods.
class StartStop extends Component {
constructor(props) {
super(props);
this.onStatusChangeReset=this.onStatusChange.bind(this);
this.onStatusChangeStart=this.onStatusChange.bind(this);
}
onStatusChange(newStatus) {
return() => {
this.props.onStatusChange(newStatus);
}
}
render() {
let {countdownStatus} = this.props;
let renderStartStopButton = () => {
if(countdownStatus === 'started') {
return <button onClick={this.onStatusChangeReset('stopped')}>Reset</button>;
} else {
return <button onClick={this.onStatusChangeStart('started')}>Start</button>
}
};
return(
<div className={styles.tt.Controls}>
{renderStartStopButton()}
</div>
)
}
}
StartStop.propTypes = {
countdownStatus: React.PropTypes.string.isRequired,
onStatusChange: React.PropTypes.func.isRequired
};

In this line in your return <StartStop countdownStatus={countdownStatus} onStatusChange={this.handleStatusChange()}/> gives the warning, the handleStatusChanged function is called on pressing a button which tries to change the state by setState keyword. whenever the state is changed render function is called again but in your case render function was in progress of returning while the render function is called again by setState keyword.