Tips for monitoring input content "live"

Question

Tips for monitoring input content "live"

Currently, I am in the process of developing a web form that includes a text field intended to receive numeric values. If the user enters non-numeric characters into this field, the form will not submit. However, there is no error message displayed to notify the user of their mistake.

My query revolves around finding a way to dynamically check the input content and provide immediate feedback to the user if it is incorrect. Ideally, I would like the border of the input field to turn green when the entry is valid, and red if invalid, accompanied by a message prompting the user to only enter numbers.

Below is a snippet of what I have implemented so far:

HTML:

<input type="text" class="btn-blue" id="testing"></input>

JS:

$('#testing').attr('placeholder', 'Enter Amount');
var useramount = $("#testing").val();
if (useramount.match(/^\d+$/)) {
   $("#testing").css({border: "2px solid #33CC00 !important"});
} 
else {
  $("#testing").css({border: "2px solid #FF0000 !important"});
  $("#testing").innerHTML = "";
  $('#testing').attr('placeholder', 'Only Numbers Please');
}

This validation technique was inspired by a similar question on Stack Overflow: Check If only numeric values were entered in input. (jQuery)

I welcome any assistance or guidance on optimizing this functionality.

javascript jquery html css

Answer 1

Answer №1

If you want to track changes while a user is typing in a field, you can utilize the input event. This event provides the element corresponding to the input element as event.target, allowing you to access the value using the 'value' property of the element.

To ensure that the input value is numerical, jQuery offers a method called isNumeric for validation purposes.

Once you have confirmed the numerical nature of the value, you can apply a specific class or style accordingly. It's important to consider cases where the input has been emptied to avoid confusion for the user.

Regarding validation messages, it's recommended not to alter the input value directly during user interaction. Instead, include a separate textual element to display conditional messages based on the validation state.

// Add error message element after input.
$('#some-number').after('<span class="error-message">Please enter numbers only!</span>')

$('#some-number').on('input', function (evt) {
  var value = evt.target.value
  
  if (value.length === 0) {
    evt.target.className = ''
    return
  }

  if ($.isNumeric(value)) {
    evt.target.className = 'valid'
  } else {
    evt.target.className = 'invalid'
  }
})

input {
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
  outline: none;
  border: 1px solid black;
}

input.valid {
  border: 1px solid green;
}

input.invalid {
  border: 1px solid red;
}

input.invalid + .error-message {
  display: initial;
}

.error-message {
  display: none;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" id="some-number">

Answer 2

If you want to track changes while a user is typing in a field, you can utilize the input event. This event provides the element corresponding to the input element as event.target, allowing you to access the value using the 'value' property of the element.

To ensure that the input value is numerical, jQuery offers a method called isNumeric for validation purposes.

Once you have confirmed the numerical nature of the value, you can apply a specific class or style accordingly. It's important to consider cases where the input has been emptied to avoid confusion for the user.

Regarding validation messages, it's recommended not to alter the input value directly during user interaction. Instead, include a separate textual element to display conditional messages based on the validation state.

// Add error message element after input.
$('#some-number').after('<span class="error-message">Please enter numbers only!</span>')

$('#some-number').on('input', function (evt) {
  var value = evt.target.value
  
  if (value.length === 0) {
    evt.target.className = ''
    return
  }

  if ($.isNumeric(value)) {
    evt.target.className = 'valid'
  } else {
    evt.target.className = 'invalid'
  }
})

input {
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
  outline: none;
  border: 1px solid black;
}

input.valid {
  border: 1px solid green;
}

input.invalid {
  border: 1px solid red;
}

input.invalid + .error-message {
  display: initial;
}

.error-message {
  display: none;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" id="some-number">

Answer 3

Answer №2

To achieve this functionality, utilize the onkeypress Event. Each time a user inputs a key while the input field is active, update the value of the input.

For instance:

var input = document.getElementById("input-box");
var inputValue = document.getElementById("input-box").value;

input.addEventListener("keypress", function() {
  inputValue = document.getElementById("input-box").value;
  // perform desired action
});

<input id="input-box"/>

I trust that I have accurately explained the process.

Answer 4

To achieve this functionality, utilize the onkeypress Event. Each time a user inputs a key while the input field is active, update the value of the input.

For instance:

var input = document.getElementById("input-box");
var inputValue = document.getElementById("input-box").value;

input.addEventListener("keypress", function() {
  inputValue = document.getElementById("input-box").value;
  // perform desired action
});

<input id="input-box"/>

I trust that I have accurately explained the process.

Answer 5

Answer №3

To implement validation logic based on user input, you can attach it to either a keypress event using jQuery like this:

$('#target').keydown(function () {
    // your validation logic here
});

Alternatively, you can also trigger the validation when the target element loses focus by using the blur event:

$("#target").blur(function() {
    // your validation logic here
});

Here's an example demonstrating both approaches:

https://jsfiddle.net/smzob72e/

Answer 6

To implement validation logic based on user input, you can attach it to either a keypress event using jQuery like this:

$('#target').keydown(function () {
    // your validation logic here
});

Alternatively, you can also trigger the validation when the target element loses focus by using the blur event:

$("#target").blur(function() {
    // your validation logic here
});

Here's an example demonstrating both approaches:

https://jsfiddle.net/smzob72e/

Answer 7

Answer №4

Here is an example of how to use vanilla JavaScript to disable the Submit button when there is no text input:

let userInput = document.getElementById('textInput'); // get the user input element
userInput.addEventListener('input', (event) => { // listen for input events
    console.log("text", userInput.value);
    if(userInput.value.length !== 0) {
        document.getElementById('submitBtn').classList.remove('disabled');
    } else {
        document.getElementById('submitBtn').classList.add('disabled');
    }
});

Answer 8

Here is an example of how to use vanilla JavaScript to disable the Submit button when there is no text input:

let userInput = document.getElementById('textInput'); // get the user input element
userInput.addEventListener('input', (event) => { // listen for input events
    console.log("text", userInput.value);
    if(userInput.value.length !== 0) {
        document.getElementById('submitBtn').classList.remove('disabled');
    } else {
        document.getElementById('submitBtn').classList.add('disabled');
    }
});

Answer 9

Answer №5

To implement a Jquery on("input") function, you can follow this example:

$(document).ready(function() {
    $('#testing')
    .attr('placeholder', 'Enter Amount')
    .on("input", function(){
        var $this = $(this);
        var useramount = $this.val();  
        if($.isNumeric(useramount)){
            $this.css("border", "2px solid green !important");
            $this.css("background", "green");
        } else {
            $this.css("border", "2px solid red !important");
            $this.css("background", "red");
            $this.val("");
            $this.attr('placeholder', 'Only Numbers Please');
        }
    });
});

This code emphasizes the background color change over the border for educational purposes.

Answer 10

To implement a Jquery on("input") function, you can follow this example:

$(document).ready(function() {
    $('#testing')
    .attr('placeholder', 'Enter Amount')
    .on("input", function(){
        var $this = $(this);
        var useramount = $this.val();  
        if($.isNumeric(useramount)){
            $this.css("border", "2px solid green !important");
            $this.css("background", "green");
        } else {
            $this.css("border", "2px solid red !important");
            $this.css("background", "red");
            $this.val("");
            $this.attr('placeholder', 'Only Numbers Please');
        }
    });
});

This code emphasizes the background color change over the border for educational purposes.

Tips for monitoring input content "live"

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Similar questions

Combining Bootstrap navbar with React Router for seamless navigation

Refresh the angular form after submitting data

Use the Segoe UI typeface on Internet Explorer for a sleek

Navigating with Google Maps and Its Pointers

Having trouble changing font color using AngularJS - what am I missing?

What is the method for adding 24 hours to a 12-hour timestamp while preserving the AM and PM designation?

Utilize Bootstrap to combine two tables within a single column efficiently

Persist the scroll position within a div even after refreshing a PHP file using AJAX

Unable to establish a websocket connection with either Amber or NPM, uncertain of the reason

When utilizing a JQuery .animate function to transition a div from 0px to 450px in height, an unintended margin is produced during the process

Managing conflicting eslint rules within the AirBNB configuration can be challenging, but here are some best

Error: Unable to access the 'questionText' property as it is undefined

What steps should I take to fix the error message "Uncaught TypeError: Class constructor m must be called with 'new'" that occurs while attempting to access a polymer v2.0 application?

Incorporating stick-to-top scroll functionality using AngularJS and ng

Utilizing distinct JavaScript, JQuery, or CSS for individual Controllers within the Codeigniter framework

When URL string parameters are sent to an MVC controller action, they are received as null values

Angular - ngbDropdownMenu items are hidden from view, but their presence is still detectable

Unsupported MIME format

gallery showcasing pictures with a prominent main image and accompanying smaller images

What is the best way to ensure that only one of two textboxes is filled out in an HTML form?