Fix ReactJS Maximum Update Depth Exceeded Error in Forms

So, I’m running into this error:Maximum update depth exceeded. This can happen when a component repeatedly calls setState inside componentWillUpdate or componentDidUpdate. ReactJS limits the number of nested updates to prevent infinite loops.

It’s driving me nuts because it seems like something is causing an infinite loop. Here’s the context: I’m trying to validate a form using React and Reactstrap, but somewhere along the way, my state keeps triggering re-renders infinitely.

My Code:

codeimport ReactJS, { Component } from "react";
import { Breadcrumb, BreadcrumbItem, Button, Form, FormGroup, Label, Input, Col, Row, FormFeedback } from "reactstrap";
import { Link } from "react-router-dom";

class Contact extends Component {
  constructor(props) {
    super(props);
    this.state = {
      firstname: "",
      lastname: "",
      telnum: "",
      email: "",
      agree: false,
      contactType: "Tel.",
      message: "",
      touched: {
        firstname: false,
        lastname: false,
        telnum: false,
        email: false,
      },
    };

    this.handleSubmit = this.handleSubmit.bind(this);
    this.handleInputChange = this.handleInputChange.bind(this);
    this.handleBlur = this.handleBlur.bind(this);
  }

  // Blur handler to update the touched state
  handleBlur = (field) => (evt) => {
    this.setState({
      touched: { ...this.state.touched, [field]: true },
    });
  };

  // Validation logic for inputs
  validate(firstname, lastname, telnum, email) {
    const errors = { firstname: "", lastname: "", telnum: "", email: "" };

    if (this.state.touched.firstname && firstname.length < 3) 
      errors.firstname = "First Name should be >= 3 characters";
    else if (this.state.touched.firstname && firstname.length > 10) 
      errors.firstname = "First Name should be <= 10 characters";

    if (this.state.touched.lastname && lastname.length < 3) 
      errors.lastname = "Last Name should be >= 3 characters";
    else if (this.state.touched.lastname && lastname.length > 10) 
      errors.lastname = "Last Name should be <= 10 characters";

    const reg = /^\d+$/;
    if (this.state.touched.telnum && !reg.test(telnum)) 
      errors.telnum = "Tel. Number should contain only numbers";

    if (this.state.touched.email && !email.includes("@")) 
      errors.email = "Email should contain '@'";

    return errors;
  }

  // Handle input changes
  handleInputChange(event) {
    const { name, value, type, checked } = event.target;
    this.setState({ [name]: type === "checkbox" ? checked : value });
  }

  // Submit handler
  handleSubmit(event) {
    console.log("Current state is: " + JSON.stringify(this.state));
    alert("Current state is: " + JSON.stringify(this.state));
    event.preventDefault();
  }

  render() {
    const errors = this.validate(
      this.state.firstname,
      this.state.lastname,
      this.state.telnum,
      this.state.email
    );

    return (
      <div className="container">
        <div className="row">
          <Breadcrumb>
            <BreadcrumbItem><Link to="/home">Home</Link></BreadcrumbItem>
            <BreadcrumbItem active>Contact Us</BreadcrumbItem>
          </Breadcrumb>
          <div className="col-12">
            <h3>Contact Us</h3><hr />
          </div>
        </div>
        <Form onSubmit={this.handleSubmit}>
          <FormGroup row>
            <Label htmlFor="firstname" md={2}>First Name</Label>
            <Col md={10}>
              <Input
                type="text"
                id="firstname"
                name="firstname"
                placeholder="First Name"
                value={this.state.firstname}
                valid={errors.firstname === ""}
                invalid={errors.firstname !== ""}
                onBlur={this.handleBlur("firstname")}
                onChange={this.handleInputChange}
              />
              <FormFeedback>{errors.firstname}</FormFeedback>
            </Col>
          </FormGroup>

          {/* Similar form groups for lastname, telnum, email */}

          <FormGroup row>
            <Col md={{ size: 10, offset: 2 }}>
              <Button type="submit" color="primary">Send Feedback</Button>
            </Col>
          </FormGroup>
        </Form>
      </div>
    );
  }
}

export default Contact;

Where’s the Infinite Loop Happening?

After digging into my code, I realized that the issue might be caused by:

1. handleBlur Method Binding Issue:
   • In the constructor, I accidentally wrote: codethis.handleBlur = this.handleBlur(this); This is incorrect because it immediately invokes the method, which leads to an infinite loop.
     Fix: I should just bind the function like this: codethis.handleBlur = this.handleBlur.bind(this);
2. State Update on Every Render:
   • If a state update gets triggered during the render method, ReactJS will keep re-rendering infinitely. So I need to make sure that my state updates (like inside handleBlur) are not indirectly triggering more renders.
3. Validation on Every Render:
   • The way I’m calling validate inside render might also cause issues. Even though the validation function doesn’t directly trigger state changes, it’s worth checking that no unnecessary re-renders are happening.

Corrected Code:

codeimport React, { Component } from "react";
import {
  Breadcrumb,
  BreadcrumbItem,
  Button,
  Form,
  FormGroup,
  Label,
  Input,
  Col,
  FormFeedback,
} from "reactstrap";
import { Link } from "react-router-dom";

class Contact extends Component {
  constructor(props) {
    super(props);

    this.state = {
      firstname: "",
      lastname: "",
      telnum: "",
      email: "",
      agree: false,
      contactType: "Tel.",
      message: "",
      touched: {
        firstname: false,
        lastname: false,
        telnum: false,
        email: false,
      },
    };

    // Binding functions correctly to this context
    this.handleSubmit = this.handleSubmit.bind(this);
    this.handleInputChange = this.handleInputChange.bind(this);
  }

  // Correctly declaring the handleBlur function
  handleBlur = (field) => (evt) => {
    this.setState({
      touched: { ...this.state.touched, [field]: true },
    });
  };

  validate(firstname, lastname, telnum, email) {
    const errors = {
      firstname: "",
      lastname: "",
      telnum: "",
      email: "",
    };

    if (this.state.touched.firstname && firstname.length < 3)
      errors.firstname = "First Name should be at least 3 characters";
    else if (this.state.touched.firstname && firstname.length > 10)
      errors.firstname = "First Name should be at most 10 characters";

    if (this.state.touched.lastname && lastname.length < 3)
      errors.lastname = "Last Name should be at least 3 characters";
    else if (this.state.touched.lastname && lastname.length > 10)
      errors.lastname = "Last Name should be at most 10 characters";

    const reg = /^\d+$/;
    if (this.state.touched.telnum && !reg.test(telnum))
      errors.telnum = "Tel. Number should contain only numbers";

    if (this.state.touched.email && !email.includes("@"))
      errors.email = "Email should contain an '@' symbol";

    return errors;
  }

  handleInputChange(event) {
    const target = event.target;
    const value = target.type === "checkbox" ? target.checked : target.value;
    const name = target.name;

    this.setState({
      [name]: value,
    });
  }

  handleSubmit(event) {
    console.log("Current state is: " + JSON.stringify(this.state));
    alert("Current state is: " + JSON.stringify(this.state));
    event.preventDefault();
  }

  render() {
    const errors = this.validate(
      this.state.firstname,
      this.state.lastname,
      this.state.telnum,
      this.state.email
    );

    return (
      <div className="container">
        <div className="row">
          <Breadcrumb>
            <BreadcrumbItem>
              <Link to="/home">Home</Link>
            </BreadcrumbItem>
            <BreadcrumbItem active>Contact Us</BreadcrumbItem>
          </Breadcrumb>
          <div className="col-12">
            <h3>Contact Us</h3>
            <hr />
          </div>
        </div>

        <Form onSubmit={this.handleSubmit}>
          <FormGroup row>
            <Label htmlFor="firstname" md={2}>
              First Name
            </Label>
            <Col md={10}>
              <Input
                type="text"
                id="firstname"
                name="firstname"
                placeholder="First Name"
                value={this.state.firstname}
                valid={errors.firstname === ""}
                invalid={errors.firstname !== ""}
                onBlur={this.handleBlur("firstname")}
                onChange={this.handleInputChange}
              />
              <FormFeedback>{errors.firstname}</FormFeedback>
            </Col>
          </FormGroup>

          <FormGroup row>
            <Label htmlFor="lastname" md={2}>
              Last Name
            </Label>
            <Col md={10}>
              <Input
                type="text"
                id="lastname"
                name="lastname"
                placeholder="Last Name"
                value={this.state.lastname}
                valid={errors.lastname === ""}
                invalid={errors.lastname !== ""}
                onBlur={this.handleBlur("lastname")}
                onChange={this.handleInputChange}
              />
              <FormFeedback>{errors.lastname}</FormFeedback>
            </Col>
          </FormGroup>

          <FormGroup row>
            <Label htmlFor="telnum" md={2}>
              Contact Tel.
            </Label>
            <Col md={10}>
              <Input
                type="tel"
                id="telnum"
                name="telnum"
                placeholder="Tel. Number"
                value={this.state.telnum}
                valid={errors.telnum === ""}
                invalid={errors.telnum !== ""}
                onBlur={this.handleBlur("telnum")}
                onChange={this.handleInputChange}
              />
              <FormFeedback>{errors.telnum}</FormFeedback>
            </Col>
          </FormGroup>

          <FormGroup row>
            <Label htmlFor="email" md={2}>
              Email
            </Label>
            <Col md={10}>
              <Input
                type="email"
                id="email"
                name="email"
                placeholder="Email"
                value={this.state.email}
                valid={errors.email === ""}
                invalid={errors.email !== ""}
                onBlur={this.handleBlur("email")}
                onChange={this.handleInputChange}
              />
              <FormFeedback>{errors.email}</FormFeedback>
            </Col>
          </FormGroup>

          <FormGroup row>
            <Col md={{ size: 6, offset: 2 }}>
              <FormGroup check>
                <Label check>
                  <Input
                    type="checkbox"
                    name="agree"
                    checked={this.state.agree}
                    onChange={this.handleInputChange}
                  />{" "}
                  <strong>May We Contact You?</strong>
                </Label>
              </FormGroup>
            </Col>
            <Col md={{ size: 3, offset: 1 }}>
              <Input
                type="select"
                name="contactType"
                value={this.state.contactType}
                onChange={this.handleInputChange}
              >
                <option>Tel.</option>
                <option>Email</option>
              </Input>
            </Col>
          </FormGroup>

          <FormGroup row>
            <Label htmlFor="message" md={2}>
              Your Feedback
            </Label>
            <Col md={10}>
              <Input
                type="textarea"
                id="message"
                name="message"
                rows="12"
                value={this.state.message}
                onChange={this.handleInputChange}
              />
            </Col>
          </FormGroup>

          <FormGroup row>
            <Col md={{ size: 10, offset: 2 }}>
              <Button type="submit" color="primary">
                Send Feedback
              </Button>
            </Col>
          </FormGroup>
        </Form>
      </div>
    );
  }
}

export default Contact;

Explanation of Fixes:

1. Binding Issue with handleBlur:
   In the original code, you were trying to bind the handleBlur function incorrectly: codethis.handleBlur = this.handleBlur(this); This caused an immediate invocation of the function, leading to errors. I removed the incorrect binding since arrow functions automatically bind this correctly.
2. Avoiding Unnecessary Renders:
   No other state-changing logic was unnecessarily triggering renders. I ensured that handleInputChange and handleBlur were correctly updating the state without causing re-renders.
3. Validation Logic Tweaks:
   The validation function now checks for minimum and maximum lengths properly and ensures the email contains '@'.
4. Form Structure and Input Handling:
   The form is properly structured to handle validation feedback with valid and invalid props for each input field.

With these changes, the code should now run without issues, and the form will behave as expected.

Final Thoughts:

By fixing the handleBlur binding and ensuring that state updates only happen where necessary, I should be able to avoid the infinite loop issue.