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I have this validate function component how I can use It to return callback funcion?

the first file only for check validity

export function checkValidity(value, rules, shouldValidat) {
   let isValid = true;

    return isValid;

the second file caller

import { checkValidity } from "../UI/CheckValidity";
let res = checkValidity(vlaue, validationRules, shouldValidat);

callback = () =>{
   alert("call back function is done");

how I can call the callback function from the first file using react js?

You need to have a callback in checkValidity function.

So you need to add callback as argument in checkValidity(value, rules, shouldValidat, callback) and then simply do:

export function checkValidity(value, rules, shouldValidat, callback) {
   let isValid = true;
   /*do your validation here and if it's okay then call callback*/
   return isValid;

Passing Functions to Components – React, Is it OK to use arrow functions in render methods? Generally speaking, yes, it is OK, and it is often the easiest way to pass parameters to callback functions. We are calling this function and setting the count piece of the state to the value of what it is currently + 1. So, this is how a child can send data back the other way, up to the parent.

You should write a function which is like ;

callback(email) {
const re = ..... => it should be validation rule 
if(re.test) {
return email;
return false;

and when you call function in other function you should give your email or other params for function param .

How to Use the setState Callback in React, is run at a later time, usually through some interaction with the child component. In the mentioned question the function to bind is a event handler and in my problem a function being called by another. In fact, my event handler (similar to the other question) was working fine without the bind , then we are not talking about the same thing.

Two callback examples:

  1. Callback when something is true callback(isValid)
  2. Callback to deal with false (if needed) errorcallback(isValid)

    export const checkValidity = (value, rules, shouldValidate, callback, errorcallback) => {
        let isValid = true; // hardcoded
        isValid ? callback(isValid) : errorcallback(isValid)
        return isValid;

How to invoke

Pass your functions as arguments 4 & 5, in this case, callback and errorcallback

val denotes a parameter passed back from the callback. in our example above were passing isValid which we are now calling val from where checkValidity() is invoked.

import { checkValidity } from "../UI/CheckValidity";
let res = checkValidity(value, validationRules, shouldValidate);

    (val) => {console.log('callback() if true!! ' + val )},
    (val) => {console.log('errorcallback() if false!!' + val}

How and Why to Bind a Callback Function in React Components, How do you call one function from another function in Reactjs? In order to execute a function from a child component, you will need to use Refs. React supports a special attribute that you can attach to any component, that's the ref attribute, it takes a callback function, and you can access the functions of the child component in the parent accessing this.refs.REF_NAME.METHOD_NAME.

Callback Function With Parameters ReactJS, ({ age: value}, this. checkAge); }; checkAge = () => { const { age } = this. state; if (age !== Unlike the class component, our function returns the view and does not need a render function. Also, the state is controlled by the React hook function useState. Later on, we will use class components in the example app. Props. We can pass data or functions down into components through props. Here’s an example:

#6 Try REACTJS Tutorial - Callbacks using Props, How and Why to Bind a Callback Function in React Components. TL;DR: Binding callbacks is a JavaScript thing. Note: Whenever your component is re-rendered, bind(this) returns a new function and passes it down your component tree. Instead a copy of the function with the switched context is returned. This copy can then be run whenever you want. Like when a button is clicked. The constructor way. Since the ‘this’ context of App is the one that handleClick() should be using, we have to use the .bind() method on it in the constructor for that component. If this line is added to the constructor, all will work as expected:

Callback Handlers · ReasonReact, Whenever you want to pass data from child to parent you pass a function as a prop to child and from child you call that function using this.props. Converting a Function to a Class . You can convert a function component like Clock to a class in five steps: Create an ES6 class, with the same name, that extends React.Component. Add a single empty method to it called render(). Move the body of the function into the render() method. Replace props with this.props in the render() body.

  • pass callback as argument to checkvalidity and call it right before return
  • maybe return the value in the callback as well ? callback(value)
  • let res = checkValidity(vlaue, validationRules, shouldValidat, this.callback);