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리액트 한 JSX: 선택한: 선택한 JSX: "" option In a React component for a <select> menu, I need to set the selected attribute on the option that reflects the application state. In render(), the optionState is passed from the state owner to the SortMenu component. The option values are passed in as props from JSON. render: function() { var options = [], optionState = this.props.optionState; this.props.options.forEach(function(option) { var selected = (optionState === option.value) ? ' selected' : ''; options.push( <option value={option.value}{selected}>{option.label}</option> ); }); // pass {options} to the select menu jsx However that triggers a syntax error on JSX compilation. Doing this gets rid of the syntax error but obviously doesn't solve the problem: var selected = (optionState === option.value) ? 'selected' : 'false'; <option value={option.value} selected={selected}>{option.label}</option> I also tried this: var selected = (optionState === option.value) ? true : false; <option value={option.value} {selected ? 'selected' : ''}>{option.label}</option> Is there a recommended way of solving this?React makes this even easier for you. Instead of defining selected on each option, you can (and should) simply write value={optionsState} on the select tag itself: <select value={optionsState}> <option value="A">Apple</option> <option value="B">Banana</option> <option value="C">Cranberry</option> </select> For more info, see the React select tag doc. Also, React automatically understands booleans for this purpose, so you can simply write (note: not recommended) <option value={option.value} selected={optionsState == option.value}>{option.label}</option> and it will output 'selected' appropriately.You could do what React warns you when you try to set the "selected" property of the <option>: Use the defaultValue or value props on <select> instead of setting selected on <option>. So, you can use options.value on the defaultValue of your selectHere is a complete solution which incorporates the best answer and the comments below it (which might help someone struggling to piece it all together): UPDATE FOR ES6 (2019) - using arrow functions and object destructuring in main component: class ReactMain extends React.Component { constructor(props) { super(props); this.state = { fruit: props.item.fruit }; } handleChange = (event) => { this.setState({ [event.target.name]: event.target.value }); } saveItem = () => { const item = {}; item.fruit = this.state.fruit; // do more with item object as required (e.g. save to database) } render() { return ( <ReactExample name="fruit" value={this.state.fruit} handleChange={this.handleChange} /> ) } } included component (which is now a stateless functional): export const ReactExample = ({ name, value, handleChange }) => ( <select name={name} value={value} onChange={handleChange}> <option value="A">Apple</option> <option value="B">Banana</option> <option value="C">Cranberry</option> </select> ) PREVIOUS ANSWER (using bind): in main component: class ReactMain extends React.Component { constructor(props) { super(props); // bind once here, better than multiple times in render this.handleChange = this.handleChange.bind(this); this.state = { fruit: props.item.fruit }; } handleChange(event) { this.setState({ [event.target.name]: event.target.value }); } saveItem() { const item = {}; item.fruit = this.state.fruit; // do more with item object as required (e.g. save to database) } render() { return ( <ReactExample name="fruit" value={this.state.fruit} handleChange={this.handleChange} /> ) } } included component (which is now a stateless functional): export const ReactExample = (props) => ( <select name={props.name} value={props.value} onChange={props.handleChange}> <option value="A">Apple</option> <option value="B">Banana</option> <option value="C">Cranberry</option> </select> ) the main component maintains the selected value for fruit (in state), the included component displays the select element and updates are passed back to the main component to update its state (which then loops back to the included component to change the selected value). Note the use of a name prop which allows you to declare a single handleChange method for other fields on the same form regardless of their type.Here is the latest example of how to do it. From react docs, plus auto-binding "fat-arrow" method syntax. class FlavorForm extends React.Component { constructor(props) { super(props); this.state = {value: 'coconut'}; } handleChange = (event) => this.setState({value: event.target.value}); handleSubmit = (event) => { alert('Your favorite flavor is: ' + this.state.value); event.preventDefault(); } render() { return ( <form onSubmit={this.handleSubmit}> <label> Pick your favorite flavor: <select value={this.state.value} onChange={this.handleChange}> <option value="grapefruit">Grapefruit</option> <option value="lime">Lime</option> <option value="coconut">Coconut</option> <option value="mango">Mango</option> </select> </label> <input type="submit" value="Submit" /> </form> ); } } 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. Since this whole thread has been giving fruit 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/TypescriptWith React 16.8. We can do this with hooks like the following example Codesandbox link import React, { useState } from "react"; import "./styles.css"; export default function App() { const options = [ "Monty Python and the Holy Grail", "Monty Python's Life of Brian", "Monty Python's The Meaning of Life" ]; const filmsByTati = [ { id: 1, title: "Jour de fête", releasedYear: 1949 }, { id: 2, title: "Play time", releasedYear: 1967 }, { id: 3, releasedYear: 1958, title: "Mon Oncle" } ]; const [selectedOption, setSelectedOption] = useState(options[0]); const [selectedTatiFilm, setSelectedTatiFilm] = useState(filmsByTati[0]); return ( <div className="App"> <h1>Select Example</h1> <select value={selectedOption} onChange={(e) => setSelectedOption(e.target.value)} > {options.map((option) => ( <option key={option} value={option}> {option} </option> ))} </select> <span>Selected option: {selectedOption}</span> <select value={selectedTatiFilm} onChange={(e) => setSelectedTatiFilm( filmsByTati.find(film => (film.id == e.target.value)) ) } > {filmsByTati.map((film) => ( <option key={film.id} value={film.id}> {film.title} </option> ))} </select> <span>Selected option: {selectedTatiFilm.title}</span> </div> ); } Simply add as first option of your select tag: <option disabled hidden value=''></option> This will become default and when you'll select a valid option will be setted on your stateMain Point - Controlled Component You are looking to set up a "Controlled Component". This will require you to set the value on the element as well as handle the on change event to update the value. https://reactjs.org/docs/forms.html#controlled-components Examples https://codepen.io/codyswartz/pen/QWqYNrY Simple Functional Component Select Example This also includes a default and grays it out. const defaultSelectValue = "Select a fruit" const SelectExample = () => { const [selected, setSelected] = useState(defaultSelectValue) return ( <> <label htmlFor="fruits">Fruits</label>{' '} <select id="fruits" name="fruits" defaultValue={selected} style={{ color: selected === defaultSelectValue ? "gray" : "black" }} onChange={e => setSelected(e.target.value)} > <option>{defaultSelectValue}</option> <option>Banana</option> <option>Apple</option> <option>Orange</option> </select> <h2>Selected: {selected}</h2> </> ) } // Usage <SelectExample /> Dynamic Reusable Example with Default This would take a collection of strings using the first as a default. const SelectExample = ({ name, items }) => { const defaultSelectValue = items[0] const [selected, setSelected] = useState(defaultSelectValue) return ( <> <label htmlFor={name}>{name}</label>{' '} <select id={name} name={name} defaultValue={selected} style={{ color: selected === defaultSelectValue ? "gray" : "black" }} onChange={e => setSelected(e.target.value)} > {items.map(item => ( <option key={item} value={item}> {item} </option> ))} </select> <h2>Selected: {selected}</h2> </> ) } // Usage <SelectExample name="fruits" items={['Select a fruit', 'Banana', 'Apple', 'Orange']} /> ***Html:*** <div id="divContainer"></div> var colors = [{ Name: 'Red' }, { Name: 'Green' }, { Name: 'Blue' }]; var selectedColor = 'Green'; ReactDOM.render(<Container></Container>, document.getElementById("divContainer")); var Container = React.createClass({ render: function () { return ( <div> <DropDown data={colors} Selected={selectedColor}></DropDown> </div>); } }); ***Option 1:*** var DropDown = React.createClass( { render: function () { var items = this.props.data; return ( <select value={this.props.Selected}> { items.map(function (item) { return <option value={item.Name }>{item.Name}</option>; }) } </select>); } }); ***Option 2:*** var DropDown = React.createClass( { render: function () { var items = this.props.data; return ( <select> { items.map(function (item) { return <option value={item.Name} selected={selectedItem == item.Name}>{item.Name}</option>; }) } </select>); } }); ***Option 3:*** var DropDown = React.createClass( { render: function () { var items = this.props.data; return ( <select> { items.map(function (item) { if (selectedItem == item.Name) return <option value={item.Name } selected>{item.Name}</option>; else return <option value={item.Name }>{item.Name}</option>; }) } </select>); } }); Use defaultValue to preselect the values for Select. <Select defaultValue={[{ value: category.published, label: 'Publish' }]} options={statusOptions} onChange={handleStatusChange} /> if you store objects in a state. class Studentinformation extends Component { constructor(props) { super(props); this.handlechange=this.handlechange.bind(this); this.handleSubmit=this.handleSubmit.bind(this); this.state={Studentinfo:{ Name:'', Skill:'Java', Address:'' }}; } handlechange(event) { const name=event.target.name; const value=event.target.value; this.setState({ Studentinfo: { ...this.state.Studentinfo, [name]:[value] }}); } handleSubmit(event) { event.preventDefault(); } render(){ return ( <div> <form onSubmit={this.handleSubmit}> <label>Name: <input type="text" name="Name" value={this.state.Studentinfo.Name} onChange={this.handlechange}></input></label> <br/> <label>Skills: <select value={this.state.Studentinfo.Skill} name="Skill" onChange={this.handlechange}> <option value="C++" >C++</option> <option value="C#">C#</option> <option value="Java">Java</option> </select> </label> <br/> <textarea value={this.state.Studentinfo.Address} onChange={this.handlechange}/> <br/> <input type="submit" value="Submit"></input> </form> </div> ); } } I've had a problem with <select> tags not updating to the correct <option> when the state changes. My problem seemed to be that if you render twice in quick succession, the first time with no pre-selected <option> but the second time with one, then the <select> tag doesn't update on the second render, but stays on the default first . I found a solution to this using refs. You need to get a reference to your <select> tag node (which might be nested in some component), and then manually update the value property on it, in the componentDidUpdate hook. componentDidUpdate(){ let selectNode = React.findDOMNode(this.refs.selectingComponent.refs.selectTag); selectNode.value = this.state.someValue; } Posting a similar answer for MULTISELECT / optgroups: render() { return( <div> <select defaultValue="1" onChange={(e) => this.props.changeHandler(e.target.value) }> <option disabled="disabled" value="1" hidden="hidden">-- Select --</option> <optgroup label="Group 1"> {options1} </optgroup> <optgroup label="Group 2"> {options2} </optgroup> </select> </div> ) } I have a simple solution is following the HTML basic. <input type="select" defaultValue="" > <option value="" disabled className="text-hide">Please select</option> <option>value1</option> <option>value1</option> </input> .text-hide is a bootstrap's class, if you not using bootstrap, here you are: .text-hide { font: 0/0 a; color: transparent; text-shadow: none; background-color: transparent; border: 0; } if you use Stateless then const IndexPage =({states, selectedState}) => { return( <select id="states" defaultValue={selectedState} name="state"> {states.map(state=> ( <option value={state.id} key={state.id}>{state.name}</option> )) } </select> ) } I got around a similar issue by setting defaultProps: ComponentName.defaultProps = { propName: '' } <select value="this.props.propName" ... So now I avoid errors on compilation if my prop does not exist until mounting.ReferenceURL : https://stackoverflow.com/questions/21733847/react-jsx-selecting-selected-on-selected-select-option