unable mapping through import react components using hooks - reactjs

Im new to react so this may be a noob question.
Im trying create a side bar that only displays links depending on if a variable is set.
but first im just trying to create a useState hook that is an array of import components and map through them with some dummy data.
The problem is it keeps tell me the component is undefined when trying to map through them.
error:TypeError: Cannot read property 'SideBarLink' of undefined
What am I doing wrong?
Also if there is a better way to do what I am trying to please lmk.
SideBar.jsx------------------------------------------------------
]
import React, { useState } from 'react';
import SideBarLink from 'react';
const SideBar = () => {
const [sidelinks, setSideLinks] = useState( SideBarLink[
{
id: 1,
name: 'Projects',
displayLink: true
},
{
id: 2,
name: 'Tickets',
displayLink: true
}
]);
const handleClick =() =>
{
console.log(sidelinks);
}
let slinks = (
<div>
<button onClick={handleClick}>button</button>
<div className="w3-sidebar w3-bar-block" >
{
sidelinks.SideBarLink.map((SideBarLink, index) =>
{
return <SideBarLink />
})
}
</div>
</div>
);
return slinks;
}
export default SideBar;
SideBarLink.jsx-------------------------------------
import React from 'react';
const SideBarLink = ( props ) => {
return (
{props.name}
)
};
export default SideBarLink;

Related

Keep track of another components state

I have a bit of a basic React question that I am having trouble googling.
I have this component which is managing the state of maximize:
import React from 'react'
import { useState } from 'react';
import './Panel.scss'
import { AiFillExperiment, AiOutlineExpandAlt } from "react-icons/ai";
const Panel = ({title}) => {
const [maximize, setMaximize] = useState(false);
return (
<div className='panel'>
<AiFillExperiment />
<p>{title}</p>
<AiOutlineExpandAlt onClick={() => setMaximize(!maximize)} />
</div>
)
}
export default Panel
and this component that needs to be able to see the value of that state:
import './App.scss';
import { useEffect, useState } from 'react';
import ReactMarkdown from 'https://esm.sh/react-markdown#7'
import remarkBreaks from 'https://esm.sh/remark-breaks#3'
import Panel from './components/Panel'
function App() {
const [markdown, setMarkdown] = useState(``)
const placeholder =
`# Welcome to my React Markdown Previewer!
## This is a sub-heading...
### And here's some other cool stuff:
Here's some code, \`<div></div>\`, between 2 backticks.
\`\`\`
// this is multi-line code:
function anotherExample(firstLine, lastLine) {
if (firstLine == '\`\`\`' && lastLine == '\`\`\`') {
return multiLineCode;
}
}
\`\`\`
You can also make text **bold**... whoa!
Or _italic_.
Or... wait for it... **_both!_**
And feel free to go crazy ~~crossing stuff out~~.
There's also [links](https://www.freecodecamp.org), and
> Block Quotes!
And if you want to get really crazy, even tables:
Wild Header | Crazy Header | Another Header?
------------ | ------------- | -------------
Your content can | be here, and it | can be here....
And here. | Okay. | I think we get it.
- And of course there are lists.
- Some are bulleted.
- With different indentation levels.
- That look like this.
1. And there are numbered lists too.
1. Use just 1s if you want!
1. And last but not least, let's not forget embedded images:
![freeCodeCamp Logo](https://cdn.freecodecamp.org/testable-projects-fcc/images/fcc_secondary.svg)
`;
useEffect(() => {
setMarkdown(placeholder)
}, [placeholder])
return (
<div className="App">
{/* Editor Container */}
<div
className={'editor-container'}
>
<Panel title='Editor' />
<textarea id='editor' onChange={(e) => setMarkdown(e.target.value)} rows="" cols="">{placeholder}</textarea>
</div>
{/* Preview Container */}
<div className='preview-container'>
<Panel title='Preview' />
<div id='preview'>
<ReactMarkdown children={markdown} remarkPlugins={[remarkBreaks]} />
</div>
</div>
</div>
);
}
export default App;
How do I go about doing this? I realize I could have it all in one component, but I would like to know how to do it with two separate components.
Thanks in advance!
Through useState + props (less recommended)
You can do that by having that state in your App component and passing the setState as a property
const App = () => {
const [maximize, setMaximize] = useState(false);
const handleToggle = (newState) => {
setState(newState)
}
return (
<div>
<Panel toggleState={toggleState} maximize={maximize} />
</div>
)
}
And in your Panel component:
const Panel = ({toggleState, maximize}) => {
const handleToggle = () => {
toggleState(!maximize)
}
return (
<AiOutlineExpandAlt onClick={handleToggle} />
)
}
Through useContext hook
useContext allows you to store variables and access them on all child components within that context provider.
MaximizeProvider.js
import React, {useState, useContext} from "react";
//creating your contexts
const MaximizeContext = React.createContext();
const MaximizeUpdateContext = React.createContext();
// create a custom hook
export const useUpdate = () => {
return useContext(MaximizeUpdateContext)
}
export const useMaximize = () => {
return usecContext(MaximizeContext)
}
//creating your component that will wrap the child components
const MaximizeProvider = ({children}) => {
const [maximize, setMaximize] = useState(false)
// Your toggle to switch the state
const toggle = () => {
setMaximize(prevState => !prevState)
}
return (
<MaximizeContext.Provider value={maximize}>
<MaximizeUpdateContext.Provider value={toggle}>
{children}
</MaximizeUpdateContext.Provider>
</MaximizeContext.Provider>
)
}
export {MAximizeProvider}
Both providers allow you to access both the state and the setState
App.js
import React, {useState} from "react";
// your context component
import {MaximizeProvider} from "./MaximizeProvider";
// a button component
import {ButtonComponent} from "./ButtonComponent";
const App = () => {
return (
<>
<MaximizeProvider>
<ButtonComponent/>
</MaximizeProvider>
< />
);
}
export {App};
in the App, you are wrapping the elements that need your context.
as long as the elements and even children of children are in the wrap, it would have access to it the same way as in the button component.
ButtonComponent.js
import {useMaximize, useUpdate} from "./MaximizeProvider";
const ButtonComponent = () => {
const toggle = useUpdate();
const state = useMaximize()
return (
<button onClick={toggle}>Click</button>
);
}
export {ButtonComponent};
I hope this helps, I am not an expert, so there might be better ways to do it, but this seems to work for me.
Use redux or react context please,
props drilling is bad practice
https://reactjs.org/docs/context.html
https://redux.js.org/

React update function from child using context

How can i update a function from a child using context??
The context
import React from 'react';
const Fin_states = React.createContext({
title: "title_title"
});
export default Fin_states;
This is the main page , the aim is update function_() using set_function_(see the states const [function_,set_function_] ) , but doing it using the context in the List_of_list child.
import React , { useState ,useContext} from 'react';
import Input_list_panel from './Input_list_panel'
import Fin_states from './Financial_instrument_states'
export default function FinancialInstruments() {
//Attribs
const context = useContext(Fin_states);
const [value, set_value] = useState({title:"initial_title"})
const [function_, set_function_] = useState(() => (data) => console.log(data))
// set_function_ is going to be represented by update_function in the context provider.
return (
<>
<Fin_states.Provider value={{ data:value, update_value:set_value,update_function:set_function_}}>
<Input_list_panel/>
</Fin_states.Provider>
<button onClick={()=>function_("data")}>
Add item in child from parent
</button>
</>
);
}
This is the file where the function is going to be modified using useEffect in this line context.update_function(()=>updated_function)
import React , { useState , useEffect, forwardRef ,useRef,useImperativeHandle, useContext } from 'react';
import Fin_states from './Financial_instrument_states'
export default function List_of_list(props) {
const [list_of_list,set_list_of_list]= useState(["data_1","data_2"]);
const context = useContext(Fin_states);
const updated_function=(data)=>{
var new_item=[...list_of_list];
new_item.push(data)
set_list_of_list(new_item);
console.log(list_of_list)
}
useEffect(() => {
/*update_function represents at set_function_ to modify function_() state , see the context
provider in the parent FinancialInstruments*/
context.update_function(()=>updated_function)
}, [])
return (
<>
<Fin_states.Consumer>
{
(context)=>{
return(
<>
<button onClick={
()=>{
updated_function("data")
}
}>
Add item in child
</button>
</>
)
}
}
</Fin_states.Consumer>
</>
);
}
The problem is that when the state of function_() is updated in the main page (FinancialInstruments functional component) it does not use the same context than updated_function() in List_of_list.
How can i have the same result that i have in List_of_list using updated_function() but using function_() in FinancialInstruments?

React native typescript: usecontext functions not firing from inside child component

I have an issue when i try to use functions from a context inside a child component in a React native android app.
Below is my code for the context, and the form component im using it in (stripped down for brevity).
The "isFormOpen" object can be read no problem from inside any children that is wrapped in the provider, but when i try to call the "toggleForm" function from the same child component, it does nothing, no console errors either.
I have another context which is identical in structure and syntax except for vairable and function names etc, and that works perfectly, so im a bit confused as to why this does not work. I removed the other context, thinking there might be some type of conflict, but didnt solve it.
AccountContext.tsx
import React, { FC, createContext, useContext, useState } from 'react';
interface AccountContextType {
isFormOpen: boolean,
toggleForm: (toggle: boolean) => void
};
export const AccountContext = createContext<AccountContextType>({
isFormOpen: false,
toggleForm: () => null
});
export const AccountContextProvider: FC = props => {
const [formOpen, setFormOpen] = useState<boolean>(false);
const toggleForm = (toggle: boolean) => {
setFormOpen(toggle);
}
const value: AccountContextType = {
isFormOpen: formOpen,
toggleForm
}
return (
<AccountContext.Provider value={value}>
{props.children}
</AccountContext.Provider>
)
}
export const useAccountContext = () => useContext(AccountContext);
TrackUploadForm.js
import React from 'react';
import { SafeAreaView } from 'react-native';
import { Button } from 'react-native-paper';
import { useAccountContext } from '../contexts/AccountContext';
import { AccountContextProvider } from '../contexts/AccountContext';
const TrackUploadForm = () => {
const accountContext = useAccountContext();
return (
<AccountContextProvider>
<SafeAreaView>
<Button onPress={() => accountContext.toggleForm(false)} mode='outlined'>Cancel</Button>
</SafeAreaView>
</AccountContextProvider>
)
};
export default TrackUploadForm;
useAccountContext is called outside the provider
export default function App() {
return (
<AccountContextProvider>
<Content />
</AccountContextProvider>
);
}
const Content = () => {
const accountContext = useAccountContext();
return (
<div className="App">
<h1>{accountContext.isFormOpen ? "true" : "false"}</h1>
<Button onPress={() => accountContext.toggleForm(false)} mode='outlined'>Cancel</Button>
</div>
);
};
accountContext.toggleForm(false) <-- always false, change it to accountContext.toggleForm(!accountContext.isFormOpen)
Together we have
https://codesandbox.io/s/cranky-panini-yo129

React horizontal timeline is not working....(I am using Next.js)

I have converted the class component to functional and used react horizontal timeline. Don't know why it's giving this output. Any help will be really appreciated. :)
Code:
import React, { useState} from 'react';
import Light from '../components/Light'
import HorizontalTimeline from 'react-horizontal-timeline'
const GrandTimeline = () => {
const VALUES = ['01/22/1998' , '01/25/1999', '01/22/2000' , '01/22/2001'];
const [ initialState, changeState] = useState({
value: 0,
previous:0958
});
return (
<Light>
<div>
<HorizontalTimeline
index={initialState.value}
indexClick={(index) => {
changeState({ value: index, previous: initialState.value });
}}
values={ VALUES } />
</div>
<div className='text-center'>
{initialState.value}
</div>
</Light>
);
}
export default GrandTimeline
Output of my code:
enter image description here

On click returns null instead of an object

It's really basic I guess. I'm trying to add onClick callback to my script & I believe I'm missing a value that would be responsible for finding the actual item.
Main script
import React from 'react';
import { CSVLink } from 'react-csv';
import { data } from 'constants/data';
import GetAppIcon from '#material-ui/icons/GetApp';
import PropTypes from 'prop-types';
const handleClick = (callback) => {
callback(callback);
};
const DownloadData = (props) => {
const { callback } = props;
return (
<>
<CSVLink
data={data}
onClick={() => handleClick(callback)}
>
<GetAppIcon />
</CSVLink>
</>
);
};
DownloadData.propTypes = {
callback: PropTypes.func.isRequired,
};
export default DownloadData;
Storybook code
import React from 'react';
import DownloadData from 'common/components/DownloadData';
import { data } from 'constants/data';
import { action } from '#storybook/addon-actions';
export default {
title: 'DownloadData',
component: DownloadData,
};
export const download = () => (
<DownloadData
data={data}
callback={action('icon-clicked')}
/>
);
So right now with this code on click in the storybook I'd get null and I'm looking for an object.
One of the potential issues I can see is that your handleClick function is stored as it is in-memory, when you import the component. That means you're keeping reference of something that doesn't exists and expects to use it when rendering the component with the callback prop.
Each instance of a component should have its own function. To fix it, move the function declaration inside the component. Like this:
const Foo = ({ callback }) => {
// handleClick needs to be inside here
const handleClick = callback => {
console.log("clicked");
callback(callback);
};
return <div onClick={() => handleClick(callback)}>Click me!</div>;
};
Check this example.
If this doesn't fix your problem, then there is something wrong with how you're implementing Storybook. Like a missing context.

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