input number maxlength with code examples

The maxlength attribute is a HTML attribute that can be applied to input fields, such as text inputs and textarea elements, to limit the maximum number of characters that can be entered by the user. This can be useful in situations where a specific input field should only accept a certain number of characters, such as a phone number or a postal code.

To use the maxlength attribute, simply add it to the input element along with a numerical value, like so:

<input type="text" maxlength="10">

This will limit the number of characters that can be entered into the input field to 10. If the user attempts to enter more than 10 characters, the input will be truncated and the remaining characters will be ignored.

It's also possible to combine the maxlength attribute with other attributes, such as the pattern attribute to create more advanced input fields. For example, the following code creates a text input that only accepts 10-digit phone numbers:

<input type="text" pattern="[0-9]{10}" maxlength="10">

In this example, the pattern attribute is set to [0-9]{10}, which means that the input field will only accept 10 digits. The maxlength attribute is set to 10, ensuring that the user can only enter 10 characters, ensuring that only a valid 10-digit phone number can be entered.

You can also use JavaScript to check the length of the input value and then perform an action based on the length. For example, the following code will disable a button if the input field is empty or has more than 10 characters:

<input type="text" id="phone-number">
<button id="submit-button" disabled>Submit</button>

<script>
const input = document.getElementById("phone-number");
const button = document.getElementById("submit-button");

input.addEventListener("input", function() {
  if (input.value.length === 0 || input.value.length > 10) {
    button.disabled = true;
  } else {
    button.disabled = false;
  }
});
</script>

In this example, an event listener is added to the input field that listens for the "input" event. When the event is triggered, the code checks the length of the input field's value. If the value is empty or has more than 10 characters, the button is disabled. Otherwise, the button is enabled.

In addition, you can also use the maxlength attribute in forms using Angular, React and Vue.js.
For example in Angular you can use the maxlength attribute in the same way as in HTML, and you can also use the [(ngModel)] directive to bind the value of the input field to a component property, and then use that property in your component's logic.

<input type="text" [(ngModel)]="phoneNumber" maxlength="10">

export class MyComponent {
  phoneNumber: string;
  // ...
}

In React you can use the maxLength prop, and you can use the value and onChange props to handle the value of the input field.

<input type="text" maxLength={10} value={this.state.phoneNumber}
In addition to using the `maxlength` attribute to limit the number of characters that can be entered into an input field, there are several other techniques that can be used to validate user input and ensure that it meets certain criteria.

One common technique is to use regular expressions, also known as regex, to validate the format of user input. Regular expressions are a powerful tool that can be used to match patterns in text, and they can be used to ensure that user input matches a specific format, such as an email address or a phone number. 

For example, the following regular expression can be used to validate an email address:

const emailRegex = /^[a-zA-Z0-9.!#$%&'+/=?^_`{|}~-]+@a-zA-Z0-9?(?:.a-zA-Z0-9?)$/;

You can use the `test()` method to check if an input value matches this regular expression.

const email = "example@gmail.com";
const isValidEmail = emailRegex.test(email);
console.log(isValidEmail); // true

Another approach to validate user input is to use a library like Formik, which is a popular library for handling forms in React. Formik provides a set of higher-order components and hooks that can be used to create and validate forms with minimal setup. Formik also integrates with other popular libraries like Yup, which can be used to create complex validation schemas.

For example, the following code uses Formik and Yup to create a form that requires the user to enter their name, email, and password, and validates that the email is in the correct format and the password is at least 8 characters long:

import { Formik, Form, Field, ErrorMessage } from "formik";
import * as Yup from "yup";

const validationSchema = Yup.object({
name: Yup.string().required("Name is required"),
email: Yup.string()
.email("Invalid email address")
.required("Email is required"),
password: Yup.string()
.min(8, "Password must be at least 8 characters")
.required("Password is required"),
});

const MyForm = () => (
<Formik
initialValues={{ name: "", email: "", password: "" }}
validationSchema={validationSchema}

{({ isSubmitting }) => (
  <Form>
    <Field name="name" type="text" placeholder="Name" />
    <ErrorMessage name="name" component="div" />
    
    <Field name="email" type="email" placeholder="Email" />
    <ErrorMessage name="email" component="div" />

    <Field name="password" type="password" placeholder="Password" />
    <ErrorMessage name="password" component="div" />
    
    <button type="submit" disabled={isSubmitting}>
      Submit
    </button>
 

Popular questions

1. What is the purpose of the maxlength attribute in HTML?

• The maxlength attribute is used to limit the maximum number of characters that can be entered into an input field, such as text inputs and textarea elements.

2. How can the maxlength attribute be used in an input field?

• The maxlength attribute can be applied to an input field by adding it to the input element along with a numerical value. For example:

<input type="text" maxlength="10">

3. Can the maxlength attribute be used in combination with other attributes?

• Yes, the maxlength attribute can be used in combination with other attributes, such as the pattern attribute to create more advanced input fields. For example, the following code creates a text input that only accepts 10-digit phone numbers:

<input type="text" pattern="[0-9]{10}" maxlength="10">

4. How can the maxlength attribute be used with JavaScript?

• The maxlength attribute can be used with JavaScript by checking the length of the input value and then performing an action based on the length. For example, the following code will disable a button if the input field is empty or has more than 10 characters:

<input type="text" id="phone-number">
<button id="submit-button" disabled>Submit</button>

<script>
const input = document.getElementById("phone-number");
const button = document.getElementById("submit-button");

input.addEventListener("input", function() {
  if (input.value.length === 0 || input.value.length > 10) {
    button.disabled = true;
  } else {
    button.disabled = false;
  }
});
</script>

5. How can the maxlength attribute be used with modern libraries?

• maxlength attribute can be used with modern libraries like Angular, React and Vue.js. For example, in React you can use the maxLength prop, and you can use the value and onChange props to handle the value of the input field. Another approach to validate user input is to use a library like Formik, which is a popular library for handling forms in React. Formik provides a set of higher-order components and hooks that can be used to create and validate forms with minimal setup. Formik also integrates with other popular libraries like Yup, which can be used to create complex validation schemas.

Tag

Validation.