Within my below example, I've a little select and a button. When I change the select value to e.g., 5 and press the button to reload the HTML select, I am wondering now why the displayed value inside the select is not reset after the jQuery load event, even if I set selected="selected" inside my HTML code?
(function($) {
$(document).ready(function() {
$('button').click(function() {
let select = $('#select');
console.log(`Value before: ${select.val()}`);
$('#wrapper').load(window.location.href + " #wrapper", function() {
let select = $('#select');
console.log(`Value after: ${select.val()}`);
});
});
});
})(jQuery);
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="wrapper">
<select id="select" name="quantity">
<option value="1">1</option>
<option value="2" selected="selected">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
</div>
<button>Load</button>
I'm trying to do a calculation, depending on the selects, an example is, calculate the number of adults per a base price.
The problem is that when I select another value in the (Select - Option) it does not update the value and still shows the first value.
Any suggestions?
values = {
adults : $('#adults').val(),
children: $('#children').val(),
listPickup: $('#pickup').val()
}
price = {
base: values.adults * 6,
child: values.children * 5,
pickup: values.listPickup * values.adults,
total : function() {
return this.base + this.child + this.pickup
}
}
$('.bookinginput').on('change', function(){
console.log(price.total())
})
<script src="https://code.jquery.com/jquery-2.2.4.min.js"></script>
<select class="bookinginput" name="adults" id="adults" >
<option value="1">1</option>
<option value="2">2</option>
</select>
<select class="bookinginput" name="children" id="children" >
<option value="3">3</option>
<option value="3">4</option>
</select>
<select class="bookinginput" name="pickup" id="pickup">
<option value="6">6</option>
<option value="7">7</option>
</select>
As everybody said, you need to recalculate. Here i did some changes to your code
Basically, every time you call total() function, it first call getProperties() which is a new method i wrote that gets the current value from the <select> objects. Then it gets the total of the updated values
price = {
base: null,
child: null,
pickup: null,
total : function() {
// Here we first update the properties with the actual value and then we get the total value
return this.getProperties().getTotal();
} ,
// Get the data from the select and update current price properties
getProperties: function(){
this.base = $('#adults').val() * 6;
this.child = $('#children').val() * 5;
this.pickup = $('#pickup').val() * $('#adults').val();
return this;
},
// function to get the total value
getTotal: function(){
return this.base + this.child + this.pickup;
}
}
$('.bookinginput').on('change', function(){
console.log(price.total())
})
<script src="https://code.jquery.com/jquery-2.2.4.min.js"></script>
<select class="bookinginput" name="adults" id="adults" >
<option value="1">1</option>
<option value="2">2</option>
</select>
<select class="bookinginput" name="children" id="children" >
<option value="3">3</option>
<option value="4">4</option>
</select>
<select class="bookinginput" name="pickup" id="pickup">
<option value="6">6</option>
<option value="7">7</option>
</select>
I think you need to update the values when the onchange event is trigger.
Otherwise, your values are set in the page load but not refresh when you call, for exemple, values.adults.
$('.bookinginput').on('change', function(){
values.adults = $('#adults').val();
values.children = $('#children').val();
values.listPickup = $('#pickup').val();
console.log(price.total())
})
Why is the <select> I create in the constructor not updated when I pick another flavor in it? The other select, as well as the text, is updated.
class ConstructorComponent extends React.Component {
constructor() {
super();
this.state = {
icecream: 'vanilla',
};
this.select = (
<select
value={this.state.icecream}
onChange={this.onChange}
>
<option value="chocolate">Chocolate</option>
<option value="vanilla">Vanilla</option>
<option value="strawberry">Strawberry</option>
</select>
);
}
onChange = event => {
this.setState({
icecream: event.target.value,
});
};
render() {
return (
<div>
Icecream flavor: {this.state.icecream}
<br />
{this.select}
<br />
<select
value={this.state.icecream}
onChange={this.onChange}
>
<option value="chocolate">Chocolate</option>
<option value="vanilla">Vanilla</option>
<option value="strawberry">Strawberry</option>
</select>
</div>
);
}
}
ReactDOM.render(
<ConstructorComponent />,
document.getElementById('container')
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="container">
<!-- This element's contents will be replaced with your component. -->
</div>
I made it work by cloning this.select in render() like so: {React.cloneElement(this.select, {value: this.state.icecream})}
But making this.select a method instead, as suggested by several answers to my question is probably better. I'll see what works best with my actual code, and not just this dumbed down example :)
Because this.state.icecream in your first select is interpreted only once, when you define this.select in the constructor. So when your ConstructorComponent rerenders a second time when its state changes, there is nothing to update in your first select.
You need to define this.select as a function returning the <select>, like this:
this.select = () => {
return (
<select
value={this.state.icecream}
onChange={this.onChange}
>
<option value="chocolate">Chocolate</option>
<option value="vanilla">Vanilla</option>
<option value="strawberry">Strawberry</option>
</select>
)
}
And call this.select() in the render.
You can also create a reference to the <select> in the render by using the prop ref:
render() {
<select
value={this.state.icecream}
onChange={this.onChange}
ref={select => (this.select = select)} // the magic happens here
>
<option value="chocolate">Chocolate</option>
<option value="vanilla">Vanilla</option>
<option value="strawberry">Strawberry</option>
</select>
}
In doing so, you don't need to define this.select as a function in your constructor.
The first select doesn't work because it's only ever rendered once, in the constructor. The second select works because it's re-rendered every time the app state updates.
If it helps, don't think of JSX elements as "instances" of actual HTML elements. Think of them as a simple means of how you want your app to look in relation to your state. If my state is "a", then I render a select with "a", and if my state is "b", then I render a select with "b", and so on.
The first select box on the page is only rendered in the constructor which is called just once, thus the component will always remain the same as it does when it is first rendered. In other words it is static. The second select box is going to be re-rendered each time the component is updated.
In order to fix your code you can change your line in the constructor to a function:
this.select = () => (
<select
value={this.state.icecream}
onChange={this.onChange}
>
<option value="chocolate">Chocolate</option>
<option value="vanilla">Vanilla</option>
<option value="strawberry">Strawberry</option>
</select>
);
Then change your return statement to call this function:
<br />
{this.select()}
<br />
JsFiddle : https://jsfiddle.net/69z2wepo/9956/
I am returning a select element in the render function in my react.js code.
But whenever I change the select value, the function in the onChange is not getting triggered.
var Hello = React.createClass({
render: function() {
return <select id="data-type" onChange={changeDataType()}>
<option selected="selected" value="user" data-type="enum">User</option>
<option value="HQ center" data-type="text">HQ Center</option>
<option value="business unit" data-type="boolean">Business Unit</option>
<option value="note" data-type="date">Try on </option>
<option value="con" data-type="number">Con</option>
</select>
}
});
React.render(<Hello/>, document.getElementById('container'));
function changeDataType() {
console.log("entered");
}
This function is getting triggered only once when the select is loaded and subsequently when I change the value, its not getting triggered.
onChange takes a function.
You are passing it changeDataType(), which is running the function changeDataType function, and setting onChange to it's return value, which is null.
Try passing the actual function, instead of evaluating the function.
<select id="data-type" onChange={changeDataType}>
Functions that trigger when a component changes should really be defined inside the component itself.
I recommend defining your function inside of your Hello component, and passing this.changeDataType to your onChange attribute, like so:
var Hello = React.createClass({
changeDataType: function() {
console.log('entered');
},
render: function() {
return <select id="data-type" onChange={this.changeDataType}>
<option selected="selected" value="user" data-type="enum">User</option>
<option value="HQ center" data-type="text">HQ Center</option>
<option value="business unit" data-type="boolean">Business Unit</option>
<option value="note" data-type="date">Try on </option>
<option value="con" data-type="number">Con</option>
</select>
}
});
Here is an updated JSFiddle that produces your expected behavior: https://jsfiddle.net/69z2wepo/9958/
Try this
<select id="data-type" onChange={()=>changeDataType()}>
I'm using react and I want to get the value of the selected option of a dropdown in react but I don't know how. Any suggestions? thanks!
My dropdown is just a select like:
<select id = "dropdown">
<option value="N/A">N/A</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
The code in the render method represents the component at any given time.
If you do something like this, the user won't be able to make selections using the form control:
<select value="Radish">
<option value="Orange">Orange</option>
<option value="Radish">Radish</option>
<option value="Cherry">Cherry</option>
</select>
So there are two solutions for working with forms controls:
Controlled Components Use component state to reflect the user's selections. This provides the most control, since any changes you make to state will be reflected in the component's rendering:
example:
var FruitSelector = React.createClass({
getInitialState:function(){
return {selectValue:'Radish'};
},
handleChange:function(e){
this.setState({selectValue:e.target.value});
},
render: function() {
var message='You selected '+this.state.selectValue;
return (
<div>
<select
value={this.state.selectValue}
onChange={this.handleChange}
>
<option value="Orange">Orange</option>
<option value="Radish">Radish</option>
<option value="Cherry">Cherry</option>
</select>
<p>{message}</p>
</div>
);
}
});
React.render(<FruitSelector name="World" />, document.body);
JSFiddle: http://jsfiddle.net/xe5ypghv/
Uncontrolled Components The other option is to not control the value and simply respond to onChange events. In this case you can use the defaultValue prop to set an initial value.
<div>
<select defaultValue={this.state.selectValue}
onChange={this.handleChange}
>
<option value="Orange">Orange</option>
<option value="Radish">Radish</option>
<option value="Cherry">Cherry</option>
</select>
<p>{message}</p>
</div>
http://jsfiddle.net/kb3gN/10396/
The docs for this are great: http://facebook.github.io/react/docs/forms.html
and also show how to work with multiple selections.
UPDATE
A variant of Option 1 (using a controlled component) is to use Redux and React-Redux to create a container component. This involves connect and a mapStateToProps function, which is easier than it sounds but probably overkill if you're just starting out.
Implement your Dropdown as
<select id = "dropdown" ref = {(input)=> this.menu = input}>
<option value="N/A">N/A</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
Now, to obtain the selected option value of the dropdown menu just use:
let res = this.menu.value;
It should be like:
import React, { useState } from "react";
export default function App() {
const getInitialState = () => {
const value = "Orange";
return value;
};
const [value, setValue] = useState(getInitialState);
const handleChange = (e) => {
setValue(e.target.value);
};
return (
<div>
<select value={value} onChange={handleChange}>
<option value="Orange">Orange</option>
<option value="Radish">Radish</option>
<option value="Cherry">Cherry</option>
</select>
<p>{`You selected ${value}`}</p>
</div>
);
}
you can see it here: https://codesandbox.io/s/quizzical-https-t1ovo?file=/src/App.js:0-572
Just use onChange event of the <select> object.
Selected value is in e.target.value then.
By the way, it's a bad practice to use id="...". It's better to use ref=">.."
http://facebook.github.io/react/docs/more-about-refs.html
As for front-end developer many time we are dealing with the forms in which we have to handle the dropdowns and we have to
use the value of selected dropdown to perform some action or the send the value on the Server, it's very simple
you have to write the simple dropdown in HTML just put the one onChange method for the selection in the dropdown
whenever user change the value of dropdown set that value to state so you can easily access it in AvFeaturedPlayList
1
remember you will always get the result as option value and not the dropdown text which is displayed on the screen
import React, { Component } from "react";
import { Server } from "net";
class InlineStyle extends Component {
constructor(props) {
super(props);
this.state = {
selectValue: ""
};
this.handleDropdownChange = this.handleDropdownChange.bind(this);
}
handleDropdownChange(e) {
this.setState({ selectValue: e.target.value });
}
render() {
return (
<div>
<div>
<div>
<select id="dropdown" onChange={this.handleDropdownChange}>
<option value="N/A">N/A</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
</div>
<div>Selected value is : {this.state.selectValue}</div>
</div>
</div>
);
}
}
export default InlineStyle;
Using React Functional Components:
const [option,setOption] = useState()
function handleChange(event){
setOption(event.target.value)
}
<select name='option' onChange={handleChange}>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
import React from 'react';
import Select from 'react-select';
const options = [
{ value: 'chocolate', label: 'Chocolate' },
{ value: 'strawberry', label: 'Strawberry' },
{ value: 'vanilla', label: 'Vanilla' },
];
class App extends React.Component {
state = {
selectedOption: null,
};
handleChange = selectedOption => {
this.setState({ selectedOption });
console.log(`Option selected:`, selectedOption);
};
render() {
const { selectedOption } = this.state;
return (
<Select
value={selectedOption}
onChange={this.handleChange}
options={options}
/>
);
}
}
And you can check it out on this site.
It is as simple as that. You just need to use "value" attributes instead of "defaultValue" or you can keep both if a pre-selected feature is there.
....
const [currentValue, setCurrentValue] = useState(2);
<select id = "dropdown" value={currentValue} defaultValue={currentValue}>
<option value="N/A">N/A</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
.....
setTimeut(()=> {
setCurrentValue(4);
}, 4000);
In this case, after 4 secs the dropdown will be auto-selected with option 4.
I was making a drop-down menu for a language selector - but I needed the dropdown menu to display the current language upon page load. I would either be getting my initial language from a URL param example.com?user_language=fr, or detecting it from the user’s browser settings. Then when the user interacted with the dropdown, the selected language would be updated and the language selector dropdown would display the currently selected language.
In the spirit of the other answers using food examples, I got all sorts of fruit goodness for you.
First up, answering the initially asked question with a basic React functional component - two examples with and without props, then how to import the component elsewhere.
Next up, the same example - but juiced up with Typescript.
Then a bonus finale - A language selector dropdown component using Typescript.
Basic React (16.13.1) Functional Component Example. Two examples of FruitSelectDropdown , one without props & one with accepting props fruitDetector
import React, { useState } from 'react'
export const FruitSelectDropdown = () => {
const [currentFruit, setCurrentFruit] = useState('oranges')
const changeFruit = (newFruit) => {
setCurrentFruit(newFruit)
}
return (
<form>
<select
onChange={(event) => changeFruit(event.target.value)}
value={currentFruit}
>
<option value="apples">Red Apples</option>
<option value="oranges">Outrageous Oranges</option>
<option value="tomatoes">Technically a Fruit Tomatoes</option>
<option value="bananas">Bodacious Bananas</option>
</select>
</form>
)
}
Or you can have FruitSelectDropdown accept props, maybe you have a function that outputs a string, you can pass it through using the fruitDetector prop
import React, { useState } from 'react'
export const FruitSelectDropdown = ({ fruitDetector }) => {
const [currentFruit, setCurrentFruit] = useState(fruitDetector)
const changeFruit = (newFruit) => {
setCurrentFruit(newFruit)
}
return (
<form>
<select
onChange={(event) => changeFruit(event.target.value)}
value={currentFruit}
>
<option value="apples">Red Apples</option>
<option value="oranges">Outrageous Oranges</option>
<option value="tomatoes">Technically a Fruit Tomatoes</option>
<option value="bananas">Bodacious Bananas</option>
</select>
</form>
)
}
Then import the FruitSelectDropdown elsewhere in your app
import React from 'react'
import { FruitSelectDropdown } from '../path/to/FruitSelectDropdown'
const App = () => {
return (
<div className="page-container">
<h1 className="header">A webpage about fruit</h1>
<div className="section-container">
<h2>Pick your favorite fruit</h2>
<FruitSelectDropdown fruitDetector='bananas' />
</div>
</div>
)
}
export default App
FruitSelectDropdown with Typescript
import React, { FC, useState } from 'react'
type FruitProps = {
fruitDetector: string;
}
export const FruitSelectDropdown: FC<FruitProps> = ({ fruitDetector }) => {
const [currentFruit, setCurrentFruit] = useState(fruitDetector)
const changeFruit = (newFruit: string): void => {
setCurrentFruit(newFruit)
}
return (
<form>
<select
onChange={(event) => changeFruit(event.target.value)}
value={currentFruit}
>
<option value="apples">Red Apples</option>
<option value="oranges">Outrageous Oranges</option>
<option value="tomatoes">Technically a Fruit Tomatoes</option>
<option value="bananas">Bodacious Bananas</option>
</select>
</form>
)
}
Then import the FruitSelectDropdown elsewhere in your app
import React, { FC } from 'react'
import { FruitSelectDropdown } from '../path/to/FruitSelectDropdown'
const App: FC = () => {
return (
<div className="page-container">
<h1 className="header">A webpage about fruit</h1>
<div className="section-container">
<h2>Pick your favorite fruit</h2>
<FruitSelectDropdown fruitDetector='bananas' />
</div>
</div>
)
}
export default App
Bonus Round: Translation Dropdown with selected current value:
import React, { FC, useState } from 'react'
import { useTranslation } from 'react-i18next'
export const LanguageSelectDropdown: FC = () => {
const { i18n } = useTranslation()
const i18nLanguage = i18n.language
const [currentI18nLanguage, setCurrentI18nLanguage] = useState(i18nLanguage)
const changeLanguage = (language: string): void => {
i18n.changeLanguage(language)
setCurrentI18nLanguage(language)
}
return (
<form>
<select
onChange={(event) => changeLanguage(event.target.value)}
value={currentI18nLanguage}
>
<option value="en">English</option>
<option value="de">Deutsch</option>
<option value="es">Español</option>
<option value="fr">Français</option>
</select>
</form>
)
}
An invaluable resource for React/Typescript
You can handle it all within the same function as following
<select className="form-control mb-3" onChange={(e) => this.setState({productPrice: e.target.value})}>
<option value="5">5 dollars</option>
<option value="10">10 dollars</option>
</select>
as you can see when the user select one option it will set a state and get the value of the selected event without furder coding require!
If you want to get value from a mapped select input then you can refer to this example:
class App extends React.Component {
constructor(props) {
super(props);
this.state = {
fruit: "banana",
};
this.handleChange = this.handleChange.bind(this);
}
handleChange(e) {
console.log("Fruit Selected!!");
this.setState({ fruit: e.target.value });
}
render() {
return (
<div id="App">
<div className="select-container">
<select value={this.state.fruit} onChange={this.handleChange}>
{options.map((option) => (
<option value={option.value}>{option.label}</option>
))}
</select>
</div>
</div>
);
}
}
export default App;
import {React, useState }from "react";
function DropDown() {
const [dropValue, setDropValue ]= useState();
return <>
<div>
<div class="dropdown">
<button class="btn btn-secondary" type="button" id="dropdownMenuButton1" data-bs-toggle="dropdown" aria-expanded="false">
{dropValue==null || dropValue=='' ?'Select Id':dropValue}
</button>
<ul class="dropdown-menu" aria-labelledby="dropdownMenuButton1">
<li><a class="dropdown-item" onClick={()=> setDropValue('Action')} href="#">Action</a></li>
<li><a class="dropdown-item" onClick={()=> setDropValue('Another action')} href="#">Another action</a></li>
<li><a class="dropdown-item" onClick={()=> setDropValue('Something else here')} href="#">Something else here</a></li>
</ul>
</div>
</div>
</>
}
export default DropDown
<select value ={this.state.value} onChange={this.handleDropdownChange}>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
As mentioned by Karen above you can just use the target value from the event triggered. Here is a small snippet of the code
`<select class="form-select py-2"
onChange={(e) => setVotersPerPage(e.target.value)}>
<option value="10">10</option>
<option value="25">25</option>
<option value="50">50</option>
</select>`