How to access a DOM element in React What is the equilvalent of document getElementById in React

Question

How do I select certain bars in react js   This is my code   var Progressbar   React createClass       getInitialState  function              return   completed  this props completed               addPrecent  function  value            this props completed    value          this setState   completed  this props completed                 render  function               var completed   this props completed          if  completed  lt  0    completed   0              return                I want to use this React component   var App   React createClass       getInitialState  function               return   baction   Progress1                handleChange  function  e            var value   e target value          console log value           this setState   baction  value                handleClick10  function  e            console log  You clicked     this state baction           document getElementById this state baction  addPrecent 10              render  function              return                lt div class  center  gt Progress Bars Demo              lt Progressbar completed  25  id  Progress1    gt                   lt h2 class  center  gt  lt  h2 gt                   lt Progressbar completed  50  id  Progress2    gt                   lt h2 class  center  gt  lt  h2 gt                   lt Progressbar completed  75  id  Progress3    gt                   lt h2 class  center  gt  lt  h2 gt                   lt span gt                       lt select name  selectbar  id  selectbar  value  this state baction  onChange  this handleChange  gt                           lt option value  Progress1  gt  Progress1 lt  option gt                           lt option value  Progress2  gt  Progress2 lt  option gt                           lt option value  Progress3  gt  Progress3 lt  option gt                       lt  select gt                       lt input type  button  onClick  this handleClick10  value   10    gt                       lt button gt  25 lt  button gt                       lt button gt -10 lt  button gt                       lt button gt -25 lt  button gt                   lt  span gt               lt  div gt                        I want to execute the handleClick10 function and perform the operation for my selected progressbar  But the result I get is    You clicked   Progress1  TypeError  document getElementById      is null   How do I select the certain Element in react js

User · Answer

Disclaimer  While the top answer is probably a better solution  as a beginner it s a lot to take in when all you want is something very simple  This is intended as a more direct answer to your original question  quot How can I select certain elements in React quot  I think the confusion in your question is because you have React components which you are being passed the id  quot Progress1 quot    quot Progress2 quot  etc  I believe this is not setting the html attribute  id   but the React component property  e g  class ProgressBar extends React Component       constructor props            super props          this state                 id  this props id     lt --- ID set from  lt ProgressBar id  quot Progress1 quot   gt                             As mentioned in some of the answers above you absolutely can use document querySelector inside of your React app  but you have to be clear that it is selecting the html output of  your components  render methods  So assuming your  render output looks like this  render          const id   this state id     return   lt div id   quot progress-bar- quot    id  gt  lt  div gt      Then you can elsewhere do a normal javascript querySelector call like this  let element   document querySelector   progress-bar-Progress1

User · Answer

Since React uses JSX code to create an HTML we cannot refer dom using regulation methods like documment querySelector or getElementById   Instead we can use React ref system to access and manipulate Dom as shown in below example   constructor props        super props       this imageRef   React createRef       create react ref    componentDidMount           console log this imageRef       acessing the attributes of img tag when dom loads     render    props    gt     const  urls description    this props image      return                 lt img                ref    this imageRef     assign the ref of img tag here                src    urls regular                alt    description                 gt

User · Answer

put it your input field ref   el    gt  this myInput   el

User · Answer

For getting the element in react you need to use ref and inside the function you can use the ReactDOM findDOMNode method   But what I like to do more is to call the ref right inside the event   lt input type  text  ref  ref   gt  this myTextInput   ref    gt    This is some good link to help you figure out

User · Answer

You can replace   document getElementById this state baction  addPrecent 10     with  this refs this state baction  addPrecent 10        lt Progressbar completed  25  ref  Progress1  id  Progress1   gt

User · Answer

You can do that by specifying the ref EDIT  In react v16 8 0 with function component  you can define a ref with useRef  Note that when you specify a ref on a function component  you need to use React forwardRef on it to forward the ref to the DOM element of use useImperativeHandle to to expose certain functions from within the function component Ex  const Child1   React forwardRef  props  ref    gt        return  lt div ref  ref  gt Child1 lt  div gt        const Child2   React forwardRef  props  ref    gt        const handleClick       gt         useImperativeHandle ref      gt            handleClick             return  lt div gt Child2 lt  div gt       const App        gt        const child1   useRef null       const child2   useRef null        return            lt  gt              lt Child1 ref  child1    gt              lt Child1 ref  child1    gt           lt   gt           EDIT  In React 16 3   use React createRef   to create your ref  class MyComponent extends React Component     constructor props        super props       this myRef   React createRef          render         return  lt div ref  this myRef    gt          In order to access the element  use  const node   this myRef current   DOC for using React createRef    EDIT However facebook advises against it because string refs have some issues  are considered legacy  and are likely to be removed in one of the future releases  From the docs   Legacy API  String Refs If you worked with React before  you might be familiar with an older API where the ref attribute is a string  like  quot textInput quot   and the DOM node is accessed as this refs textInput  We advise against it because string refs have some issues  are considered legacy  and are likely to be removed in one of the future releases  If you re currently using this refs textInput to access refs  we recommend the callback pattern instead   A recommended way for React 16 2 and earlier is to use the callback pattern   lt Progressbar completed  25  id  quot Progress1 quot  ref   input    gt   this Progress 0    input     gt    lt h2 class  quot center quot  gt  lt  h2 gt    lt Progressbar completed  50  id  quot Progress2 quot  ref   input    gt   this Progress 1    input     gt      lt h2 class  quot center quot  gt  lt  h2 gt    lt Progressbar completed  75  id  quot Progress3 quot  ref   input    gt   this Progress 2    input     gt   DOC for using callback  Even older versions of react defined refs using string like below  lt Progressbar completed  25  id  quot Progress1 quot  ref  quot Progress1 quot   gt        lt h2 class  quot center quot  gt  lt  h2 gt        lt Progressbar completed  50  id  quot Progress2 quot  ref  quot Progress2 quot   gt          lt h2 class  quot center quot  gt  lt  h2 gt        lt Progressbar completed  75  id  quot Progress3 quot  ref  quot Progress3 quot   gt   In order to get the element just do var object   this refs Progress1   Remember to use this inside an arrow function block like  print        gt      var object   this refs Progress1       and so on

[javascript] How to access a DOM element in React? What is the equilvalent of document.getElementById() in React

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