Create Form And Validation In ReactJS

Introduction

In this article, we will learn how to Create Form and Form validation in React Application 

Steps to follow,

Now we will start by creating a new project for mock web service. 

Step 1 

Create an Angular project setup using the below commands or however, you create your React app. 

npx create-react-app projectname

Example

npx create-react-app sample-form 

Create Form And Validation In ReactJS

Step 2 - Installing React Bootstrap 

Open a new terminal and run the following below commands. 

Install Bootstrap as a dependency in your app,

npm install react-bootstrap bootstrap 

Create Form And Validation In ReactJS

In App.js we will import bootstrap.min.css.

import "bootstrap/dist/css/bootstrap.min.css"; 

Step 3 - Add Form Field

Now we will add Formvalue field and validation.

constructor() {
    super();
    this.state = {
        form: {
            name: "",
            email: "",
            phone: "",
            password: "",
            gender: null,
            language: [],
        },
        formErrors: {
            name: null,
            email: null,
            phone: null,
            password: null,
            gender: null,
            language: null,
        },
    };
    this.language = [{
        value: "english",
        label: "English"
    }, {
        value: "Tamil",
        label: "Tamil"
    }, {
        value: "hindi",
        label: "Hindi"
    }, ];
}

We have Render Boostrap Card Design in App.js 

render() { 
    const { form, formErrors } = this.state; 
    return ( 
      <> 
        <div class="container-fluid"> 
          <div class="card mt-4"> 
            <div class="card-header card-no-bg d-flex align-items-center justify-content-between"> 
              Register Form 
            </div> 
            <div class="card-body"></div> 
        </div> 
    ); 
}

Step 4

Now we will Implement validation in Fields,

validateField = (name, value, refValue) => {
    let errorMsg = null;
    switch (name) {
        case "name":
            if (!value) errorMsg = "Please enter Name.";
            break;
        case "email":
            if (!value) errorMsg = "Please enter Email.";
            else if (!/^(([^<>()[\]\\.,;:\s@"]+(\.[^<>()[\]\\.,;:\s@"]+)*)|(".+"))@(([[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/.test(value)) errorMsg = "Please enter valid Email.";
            break;
        case "phone":
            if (!value) errorMsg = "Please enter Phone.";
            break;
        case "gender":
            if (!value) errorMsg = "Please select Gender.";
            break;
        case "password":
            if (!value) errorMsg = "Please enter Password.";
            else if (refValue && value !== refValue) errorMsg = "Password and Confirm Password does not match.";
            break;
        case "language":
            if (value.length === 0) errorMsg = "Please select Language.";
            break;
        default:
            break;
    }
    return errorMsg;
};

Step 5

Now we can handle the Change Event method on Form here.

Now we have changed to the changeValue event method to validate the value after the setState.

changeValue = (e) => {
    const {
        name,
        value,
        checked
    } = e.target;
    const {
        form,
        formErrors
    } = this.state;
    let formObj = {};
    if (name === "language") {
        // handle the change event of language 
        if (checked) {
            // push selected value in list 
            formObj = {
                ...form
            };
            formObj[name].push(value);
        } else {
            // remove unchecked value from the list 
            formObj = {
                ...form,
                [name]: form[name].filter((x) => x !== value),
            };
        }
    } else {
        // handle change event except language field 
        formObj = {
            ...form,
            [name]: value,
        };
    }
    this.setState({
        form: formObj
    }, () => {
        if (!Object.keys(formErrors).includes(name)) return;
        let formErrorsObj = {};
        if (name === "password") {
            let refValue = this.state.form[name === "password"];
            const errorMsg = this.validateField(name, value, refValue);
            formErrorsObj = {
                ...formErrors,
                [name]: errorMsg
            };
            if (!errorMsg && refValue) {
                formErrorsObj.confirmPassword = null;
                formErrorsObj.password = null;
            }
        } else {
            const errorMsg = this.validateField(name, name === "language" ? this.state.form["language"] : value);
            formErrorsObj = {
                ...formErrors,
                [name]: errorMsg
            };
        }
        this.setState({
            formErrors: formErrorsObj
        });
    });
};

Step 6

Next, we have to Render the Form Design,

render() {
    const {
        form,
        formErrors
    } = this.state;
  return ( 
     <>
     <div class="container-fluid">
       <div class="card mt-4">
         <div class="card-header card-no-bg d-flex align-items-center justify-content-between"> Register Form </div>
         <div class="card-body">
           <div className="row mb-2">
             <div className="col-md-6">
               <div className="form-group">
                 <label> Name: <span className="asterisk">*</span>
                 </label>
                 <input className="form-control" type="text" name="name" value={form.name} onChange={this.changeValue} onBlur={this.changeValue} /> {formErrors.name && ( <span className="err">{formErrors.name}</span> )}
               </div>
               <div className="form-group mt-1">
                 <label className="mr-3"> Gender: <span className="asterisk">*</span>
                 </label>
                 <div className="form-control border-0 p-0 pt-1">
                   <label className="mr-2">
                     <input type="radio" name="gender" value="male" checked={form.gender==="male" } onChange={this.changeValue} />{" "} Male </label>
                   <label>
                     <input type="radio" name="gender" value="female" checked={form.gender==="female" } onChange={this.changeValue} />{" "} Female </label>
                 </div> {formErrors.gender && ( <span className="err">{formErrors.gender}</span> )}
               </div>
               <div className="form-group">
                 <label> Password: <span className="asterisk">*</span>
                 </label>
                 <input className="form-control" type="password" name="password" value={form.password} onChange={this.changeValue} onBlur={this.changeValue} /> {formErrors.password && ( <span className="err">{formErrors.password}</span> )}
               </div>
             </div>
             <div className="col-md-6">
               <div className="form-group">
                 <label> Email: <span className="asterisk">*</span>
                 </label>
                 <input className="form-control" type="text" name="email" value={form.email} onChange={this.changeValue} onBlur={this.changeValue} /> {formErrors.email && ( <span className="err">{formErrors.email}</span> )}
               </div>
               <div className="form-group">
                 <label> Phone: <span className="asterisk">*</span>
                 </label>
                 <input className="form-control" type="text" name="phone" value={form.phone} onChange={this.changeValue} onBlur={this.changeValue} onKeyPress={this.validatePhoneNumber} /> {formErrors.phone && ( <span className="err">{formErrors.phone}</span> )}
               </div>
               <div className="form-group mt-2">
                 <label className="mr-3"> Language: <span className="asterisk">*</span>
                 </label>
                 <div className="form-control border-0 p-0 pt-1"> {this.language.map((x, i) => { return ( <label key={i} className="mr-2">
                     <input type="checkbox" name="language" value={x.value} checked={form.language.includes(x.value)} onChange={this.changeValue} />{" "} {x.label} </label> ); })} </div> {formErrors.language && ( <span className="err">{formErrors.language}</span> )}
               </div>
             </div>
           </div>
           <div className="form-group">
             <input type="button" className="btn btn-primary" value="Submit" onClick={this.handleSubmit} />
           </div>
         </div>
       </div>
     </div>undefined
   </>
  );
}

Add Phone number validation method below,

validatePhoneNumber = (evt) => {
    var theEvent = evt || window.event;
    // Handle paste 
    if (theEvent.type === "paste") {
        key = theEvent.clipboardData.getData("text/plain");
    } else {
        // Handle key press 
        var key = theEvent.keyCode || theEvent.which;
        key = String.fromCharCode(key);
    }
    var regex = /[0-9]|\./;
    if (!regex.test(key)) {
        theEvent.returnValue = false;
        if (theEvent.preventDefault) theEvent.preventDefault();
    }
};

Now finally we need to change the submit Function as below,

validateForm = (form, formErrors, validateFunc) => {
    const errorObj = {};
    Object.keys(formErrors).map((x) => {
        let refValue = null;
        if (x === "password") {
            refValue = form[x === "password"];
        }
        const msg = validateFunc(x, form[x], refValue);
        if (msg) errorObj[x] = msg;
    });
    return errorObj;
};
handleSubmit = () => {
    const {
        form,
        formErrors
    } = this.state;
    const errorObj = this.validateForm(form, formErrors, this.validateField);
    console.log(errorObj, "value ", form);
    if (Object.keys(errorObj).length !== 0) {
        this.setState({
            formErrors: {
                ...formErrors,
                ...errorObj
            }
        });
        return false;
    }
};

Step 7

Now we will run the application,

Npm run start 

On successful execution of the above command, it will show the browser, 

Create Form And Validation In ReactJS

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