How Can I Prevent HTML Encoding Loss When Retrieving Values from Input Fields in JavaScript?

HTML Encoding Loss in Input Field Attribute Retrieval

In JavaScript, retrieving the value of a hidden field for display in a textbox can present an encoding issue. Consider the following example:

<input>

When using jQuery to retrieve the value from the hidden field, JavaScript loses its encoding:

$('#hiddenId').attr('value')

The desired output is "chalk & cheese" with the literal "&" retained.

Solution

To address this issue, we introduce the following functions:

function htmlEncode(value) {
  return $('<textarea/>').text(value).html();
}

function htmlDecode(value) {
  return $('<textarea/>').html(value).text();
}

These functions create an in-memory textarea element, set its inner text, and then retrieve the encoded contents (htmlEncode) or the decoded inner text (htmlDecode). The element never exists on the DOM.

Example Usage

The following code demonstrates how to use these functions:

let encodedValue = htmlEncode('chalk & cheese');
console.log(encodedValue); // Outputs "chalk & cheese"

let decodedValue = htmlDecode(encodedValue);
console.log(decodedValue); // Outputs "chalk & cheese"

By utilizing these functions, you can effectively maintain HTML encoding when retrieving values from input fields in JavaScript.

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