how I call back function using reactjs

Question

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?

pass callback as argument to checkvalidity and call it right before return — Joy Biswas
– Joy Biswas, Commented Nov 26, 2018 at 10:49

TeaNyan · Accepted Answer · 2018-11-26 10:50:43Z

1

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*/
   callback();
   return isValid;
}

answered Nov 26, 2018 at 10:50

TeaNyan

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2 Comments

Fawzi Over a year ago

maybe return the value in the callback as well ? callback(value)

Marwan Al-Masaeid Over a year ago

let res = checkValidity(vlaue, validationRules, shouldValidat, this.callback);

Alican Çelik · Accepted Answer · 2018-11-26 11:43:16Z

1

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 .

answered Nov 26, 2018 at 11:43

Alican Çelik

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Comments

Luke Walker · Accepted Answer · 2018-11-27 11:29:42Z

Two callback examples:

Callback when something is true callback(isValid)

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);

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

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