How to create a custom form validation and display required Error message upon handle input change in Lightning web component

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Hey guys, today in this post we are going to learn about How to create a custom form validation and display required Error message upon handle input change in Lightning web component – LWC.

Files we used in this post example:-

lwcFormValidation.html	Lightning Web Component HTML	Template HTML file for used to write HTML element for user interface..
lwcFormValidation.js	Lightning Web Component JavaScript	It is holding Form Validation function that is display the required Error message on handle changing lightning input field.
lwcFormValidation.js-meta.xml	XML Meta File	It is used for where this lightning web component you want to exposed…

Don’t forget to check out:- Custom Validation in a Lightning Input Field on Click Button in Lightning Component Salesforce Click Here For More Information

Live Demo

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Step 1:- Create Lightning Web Component : lwcFormValidation.html

SFDX:Lightning Web Component >> New >> lwcFormValidation.html

lwcFormValidation.html [Lightning Web Component HTML]

  <template>
    <lightning-card title="Create a custom form validation in Lightning web component - LWC" icon-name="custom:custom12" size="small"> 
        <div class="slds-grid slds-wrap">
            <div class="slds-col slds-size_6-of-12 slds-p-horizontal--medium slds-m-bottom--medium">
               <lightning-Input type="text" label="First Name" value={firstName} name="firstName" class="firstName" onchange={handleChangeValidation}></lightning-input>
            </div>
            
            <div class="slds-col slds-size_6-of-12 slds-p-horizontal--medium slds-m-bottom--medium">
               <lightning-Input type="text"  label="Last Name" value={lastName} name="lastName" class="lastName" onchange={handleChangeValidation}></lightning-input>
            </div>
            
            <div class="slds-col slds-size_6-of-12 slds-p-horizontal--medium slds-m-bottom--medium">
               <lightning-Input type="text" label="Email" value={userEmail} name="userEmail" class="userEmail" onchange={handleChangeValidation}></lightning-input>
            </div>
            
            <div class="slds-col slds-size_6-of-12 slds-p-horizontal--medium slds-m-bottom--medium">
               <lightning-Input type="phone" label="Phone" value={userPhone} name="userPhone" class="userPhone" onchange={handleChangeValidation}></lightning-input>
            </div>
            
            <div class="slds-col slds-size_6-of-12 slds-p-horizontal--medium slds-m-bottom--medium">
               <lightning-input type="checkbox" label="Status" name="statusCheckbox" class="statusActive" onchange={handleChangeValidation}></lightning-input>
            </div>
            
            
         </div>

<br/><br/>
    <p><img src="https://www.w3web.net/wp-content/uploads/2021/05/thumbsUpLike.png" width="25" height="25" style="vertical-align:top; margin-right:10px;"/> <strong> <span style="font-size:15px; font-style:italic; display:inline-block; margin-right:5px;">Don't forget to check out:-</span> <a href="https://www.w3web.net/" target="_blank" style="text-decoration:none;" rel="noopener noreferrer">An easy way to learn step-by-step online free tutorial, To know more Click  <span style="color:#ff8000; font-size:18px;">Here..</span></a></strong></p>
    </lightning-card>
</template>

<lightning-card title="Create a custom form validation in Lightning web component - LWC" icon-name="custom:custom12" size="small">

<lightning-Input type="text" label="First Name" value={firstName} name="firstName" class="firstName" onchange={handleChangeValidation}></lightning-input>

</div>

<lightning-Input type="text" label="Last Name" value={lastName} name="lastName" class="lastName" onchange={handleChangeValidation}></lightning-input>

</div>

<lightning-Input type="text" label="Email" value={userEmail} name="userEmail" class="userEmail" onchange={handleChangeValidation}></lightning-input>

</div>

<lightning-Input type="phone" label="Phone" value={userPhone} name="userPhone" class="userPhone" onchange={handleChangeValidation}></lightning-input>

</div>

<lightning-input type="checkbox" label="Status" name="statusCheckbox" class="statusActive" onchange={handleChangeValidation}></lightning-input>

</div>

<p><img src="https://www.w3web.net/wp-content/uploads/2021/05/thumbsUpLike.png" width="25" height="25" style="vertical-align:top; margin-right:10px;"/> <strong> <span style="font-size:15px; font-style:italic; display:inline-block; margin-right:5px;">Don't forget to check out:-</span> <a href="https://www.w3web.net/" target="_blank" style="text-decoration:none;" rel="noopener noreferrer">An easy way to learn step-by-step online free tutorial, To know more Click <span style="color:#ff8000; font-size:18px;">Here..</span></a></strong></p>

</lightning-card>

</template>

Step 2:- Create Lightning Web Component : lwcFormValidation.js

SFDX:Lightning Web Component >> New >> lwcFormValidation.js

lwcFormValidation.js [LWC JavaScript File]

  import { LightningElement } from 'lwc';

export default class LwcFormValidation extends LightningElement {

    handleChangeValidation(event){
      let getFirstName = event.target.name;
      let getLstName = event.target.name;
      let getUserEmail = event.target.name;
      let getUserPhone = event.target.name;
      let getStatusActive = event.target.name;
      let getCityName = event.target.name;


      if(getFirstName === "firstName"){
          let firstName = this.template.querySelector('.firstName');
          let firstNameVal = firstName.value;
          if(!firstNameVal){
            firstName.setCustomValidity('Please Enter the First Name');
          }else{
            firstName.setCustomValidity('');
          }
          firstName.reportValidity();
      }


      else if(getLstName === "lastName"){
        let lastName = this.template.querySelector('.lastName');
        let lastNameVal = lastName.value;
        if(!lastNameVal){
            lastName.setCustomValidity('Please Enter the Larst Name');
        }else{
            lastName.setCustomValidity('');
        }
        lastName.reportValidity();
       }

      
       else if(getUserEmail === "userEmail"){
        let userEmail = this.template.querySelector('.userEmail');
        let userEmailVal = userEmail.value;
        if(!userEmailVal){
            userEmail.setCustomValidity('Please Enter the Email Id');
        }else{
            userEmail.setCustomValidity('');
        }
        userEmail.reportValidity();
       }


       else if(getUserPhone === "userPhone"){
        let userPhone = this.template.querySelector('.userPhone');
        let userPhoneVal = userPhone.value;
        if(!userPhoneVal){
            userPhone.setCustomValidity('Please Enter the Email Id');
        }else{
            userPhone.setCustomValidity('');
        }
        userPhone.reportValidity();
       }


       else if(getStatusActive === "statusCheckbox"){
        let statusCheckbox = this.template.querySelector('.statusActive');
        let statusCheckboxVal = statusCheckbox.checked;
        if(!statusCheckboxVal){
            statusCheckbox.setCustomValidity('Please Check Mark the Status Checkbox');
        }else{
            statusCheckbox.setCustomValidity('');
        }
        statusCheckbox.reportValidity();
       }        

    }

}

import { LightningElement } from 'lwc';

export default class LwcFormValidation extends LightningElement {

handleChangeValidation(event){

let getFirstName = event.target.name;

let getLstName = event.target.name;

let getUserEmail = event.target.name;

let getUserPhone = event.target.name;

let getStatusActive = event.target.name;

let getCityName = event.target.name;

if(getFirstName === "firstName"){

let firstName = this.template.querySelector('.firstName');

let firstNameVal = firstName.value;

if(!firstNameVal){

firstName.setCustomValidity('Please Enter the First Name');

}else{

firstName.setCustomValidity('');

}

firstName.reportValidity();

}

else if(getLstName === "lastName"){

let lastName = this.template.querySelector('.lastName');

let lastNameVal = lastName.value;

if(!lastNameVal){

lastName.setCustomValidity('Please Enter the Larst Name');

}else{

lastName.setCustomValidity('');

}

lastName.reportValidity();

}

else if(getUserEmail === "userEmail"){

let userEmail = this.template.querySelector('.userEmail');

let userEmailVal = userEmail.value;

if(!userEmailVal){

userEmail.setCustomValidity('Please Enter the Email Id');

}else{

userEmail.setCustomValidity('');

}

userEmail.reportValidity();

}

else if(getUserPhone === "userPhone"){

let userPhone = this.template.querySelector('.userPhone');

let userPhoneVal = userPhone.value;

if(!userPhoneVal){

userPhone.setCustomValidity('Please Enter the Email Id');

}else{

userPhone.setCustomValidity('');

}

userPhone.reportValidity();

}

else if(getStatusActive === "statusCheckbox"){

let statusCheckbox = this.template.querySelector('.statusActive');

let statusCheckboxVal = statusCheckbox.checked;

if(!statusCheckboxVal){

statusCheckbox.setCustomValidity('Please Check Mark the Status Checkbox');

}else{

statusCheckbox.setCustomValidity('');

}

statusCheckbox.reportValidity();

}

Step 3:- Create Lightning Web Component : lwcFormValidation.js-meta.xml

SFDX:Lightning Web Component >> New >> lwcFormValidation.js-meta.xml

lwcFormValidation.js-meta.xml [LWC Meta Data XML]

 <?xml version="1.0" encoding="UTF-8"?>
<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata">
    <apiVersion>45.0</apiVersion>
    <isExposed>true</isExposed>
    <targets>
        <target>lightning__AppPage</target>
        <target>lightning__RecordPage</target>
        <target>lightning__HomePage</target>
        <target>lightning__Tab</target>
      </targets>
</LightningComponentBundle>