jquery check input

jQuery Check Input#

jQuery is a popular JavaScript library that simplifies HTML document traversing, event handling, and animation for rapid web development. One of the tasks jQuery can handle is checking input fields for specific conditions using selectors and functions.

Checking if an Input Field is Empty#

To check if an input field is empty using jQuery, you can use the .val() method to get the value of the input field and compare it with an empty string using the length property. If the length is 0, then the input field is empty.

      $('input[type="text"]').blur(function() {
        if ($(this).val().length === 0) {
          $(this).css('border', '1px solid red');
        }
      });
    

In the example above, we attach a blur event listener to all input fields of type text. When the input field loses focus, the function checks if the value length is 0 and adds a red border to the input field if it is.

Checking if an Input Field Contains a Specific Value#

To check if an input field contains a specific value using jQuery, you can also use the .val() method to get the value of the input field and compare it with the specific value using the equals operator.

      $('input[type="text"]').blur(function() {
        if ($(this).val() === 'example') {
          $(this).css('background-color', 'yellow');
        }
      });
    

In the example above, we attach a blur event listener to all input fields of type text. When the input field loses focus, the function checks if the value is equal to 'example' and changes the background color of the input field to yellow if it is.

Checking if an Input Field Contains a Valid Email Address#

To check if an input field contains a valid email address using jQuery, you can use a regular expression to match the email address format and the .val() method to get the value of the input field.

      $('input[type="email"]').blur(function() {
        var email = $(this).val();
        var pattern = /^[^ ]+@[^ ]+\.[a-z]{2,3}$/;
        if (!email.match(pattern)) {
          $(this).css('border', '1px solid red');
        }
      });
    

In the example above, we attach a blur event listener to all input fields of type email. When the input field loses focus, the function gets the value of the input field and matches it with a regular expression that checks if the email address format is valid. If the email address is not valid, it adds a red border to the input field.