I've got a form, where I wanna set in the state (setEducation for example) incoming value from the input. I use onChange, but this causes the component to be rendered each time I make a change to the input field. What is the right way to fix the problem?
<form id="loginform" onSubmit={onBecomeDoctorRequestHandler} >
<div className="form-group mb-3">
<label>Education</label>
<input
type="text"
className="form-control"
required
this onChange causes the placeholder="Harvard"
component to be rendered onChange={(event) => setEducation(event.target.value.trim())}
/>
<small className="text-danger form-text">
{educationError}
</small>
</div>
As-is all your form elements will re-render when any form element changes because the "value" of onClick is a new function each time the component runs (renders).
To fix that, wrap the onClick function in a useCallback. The useCallback will preserve the "value" of the function across renders, so only the elements that needs to be re-rendered will be.
Related
anyone can point me to an example of a react multiple checkboxes validation? I have some questions, every one of them has a checkbox when it's done and when all are checked, a continue button must be activated.. I know how to do this with only one checkbox, but don't know how to handle more of them. I would rather do this in plain react and not by installing any package. Any help will be appreciated.
You can control all your inputs using useState. Example for two inputs.
import React, { useState } from "react"
const ControlledCheckboxes = () => {
const [ firstCheckbox, setFirstCheckbox ] = useState(false);
const [ secondCheckbox, setSecondCheckbox ] = useState(false);
return(
<form>
<div >
<div className="form-check">
<input type="checkbox" id="first" className="form-check-input"
onClick={()=>setFirstCheckbox(!firstCheckbox)}
value={firstCheckbox}
/>
<label className="form-check-label" htmlFor="first">FIRST</label>
</div>
<div className="form-check">
<input type="checkbox" id="second" className="form-check-input"
onClick={()=>setSecondCheckbox(!secondCheckbox)}
value={secondCheckbox}
/>
<label className="form-check-label" htmlFor="second">SECOND</label>
</div>
</div>
<button type="submit" className="btn btn-outline-success" disabled={ !(firstCheckbox && secondCheckbox) } >SUBMIT</button>
</form>
)
};
You can achieve this by using controlled inputs.
Basically you would make the value of the checkboxes correspond to variables in the state of your component. After that it is as simple as if (boolean1 && boolean2) with a conditionally rendered save button.
Controlled inputs
Conditional rendering
You can achieve most of what you want with just HTML.
<form>
<input type="checkbox" required />
<input type="checkbox" required />
<button>submit</button>
</form>
The form cannot be submitted until all checkboxes are checked.
Let's say that's not enough, you want to access the form validity in your render logic to apply styles or whatever so you need component state.
const [valid, setValid] = useState(false);
All form control change events bubble up to their form (unless explicitly stopped). We can spy on form control changes by adding a change event listener that updates component state to the form element.
event => setValid(event.target.form.checkValidity())
If your form isn't as simple as my example and you need to specifically check certain checkboxes you can find all form controls in event.target.form.elements. You can use the elements property to not even need HTML form validation.
event => setValid(Array.from(event.target.form.elements).every(
input => input.type !== 'checkbox' || input.checked
))
You can then pass valid as a prop to your submit button.
When I click on Submit, it gives an error "required". But when i type text it doesn't take first character. On entering first character it only removes "required" message.
Can you please tell me why it is not showing first character.
<div className="input-field">
<label htmlFor="state">State</label>
<input
placeholder="State"
name="state"
autoComplete="off"
type="text"
value={state}
onChange = { e => setState(e.target.value)}
ref={register({required:'required'})}
/>
<span className="error">{errors.state && errors.state.message}</span>
</div>
It's probably related to the usage of react-hook-form with your custom controlled logic (value and onChange).
If you don't need the input to be controlled, I would recommend dropping the value and onChange props from the input, as they seem to be conflicting with the package.
Most likely, because setState is an asynchronous method. Try to add the async on your onChange function and await this.setState(). It should capture all the input characters.
I have an input whose value I want to store in a React variable.
<div>
<label>Nombre Completo: </label>
<input style={eachBit} required id='name' type='text' placeholder='Zeus Aurel'></input>
</div>
Without the complications of constructor or classes, I can't find anything useful anywhere. I know nothing of reactjs, please help.
onChange event allows value to be stored in state. Here is how input value is stored in a state named inputValue.
<input
onChange={e => this.setState({ inputValue: e.target.value }))
/>
Are you asking about the way to change/insert a HTML element as a variable ?
Hope this topic can help you : Insert HTML with React Variable Statements (JSX)
There are two ways you can get input changes in your React app.
One is by using
<input type="text" onChange={this.handleChange} />
The other was is
<form onChange={this.handleChange} onSubmit={this.handleChange} />
...
</form>
When you should use first one and when the other one.
The reason that there are two ways is because there are more than the two ways. You can do this too:
<div onChange={this.handleChange}>
<form>
<input />
</form>
</div>
I'd argue that the first approach is better because the handler receives the event as early as possible and possibly because the binding between the input and the component state is encoded within the render function, but that depends on what the handler would look like.
I'm using switches component (designed by Materialize) inside React components, and I'd like to know, how could I get the value when the user has changed the switch (on/of).
<div className="switch right">
<label>
Any
<input type="checkbox" onChange={() => alert('changed')}/>
<span className="lever"></span>
All
</label>
</div>
I tried to set a onChange event to verify if I can, at least, get when it's triggered.
As a start, I would recommend using react-materialize, which has been written into components for react here https://react-materialize.github.io/#/forms.
I guess the problem is that onChange works only for JSX, and from your code it looks like you are using plain HTML?
I have added your onChange event into my JSX and it works as expected.
If you used react-materialize, your code would look something like this:
<Input name='on' type='switch' onLabel='Any' offLabel='All' onChange={() => alert('changed')}/>