How to Determine the Size of a JavaScript String in Bytes

Determining the Size of a JavaScript String in Bytes

JavaScript strings store characters using UCS-2 encoding, typically occupying two bytes per character. However, the exact byte size can vary depending on the JavaScript implementation, page encoding, and content-type.

To reliably determine the size of a JavaScript string in bytes, consider using the following approach:

<code class="javascript">const string = 'This is a sample string.';

// Create a Blob object from the string
const blob = new Blob([string]);

// Retrieve the byte size of the Blob
const byteSize = blob.size;</code>

In this code, the Blob constructor takes an array containing the string as an argument and creates a binary data object. The .size property of the Blob provides the byte size of the data it contains, including the string.

Here are a few examples to demonstrate the use of this approach:

<code class="javascript">console.info(
  new Blob(['?']).size,                             // 4
  new Blob(['?']).size,                             // 4
  new Blob(['??']).size,                           // 8
  new Blob(['??']).size,                           // 8
  new Blob(['I\'m a string']).size,                  // 12

  // Handling strings with lone characters in the surrogate pair range:
  new Blob([String.fromCharCode(55555)]).size,       // 3
  new Blob([String.fromCharCode(55555, 57000)]).size // 4 (not 6)
);</code>

By using this method, you can accurately determine the byte size of a JavaScript string, regardless of the JavaScript implementation, page encoding, or content-type.

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