Error: data after transformation must be a string, an arraybuffer, a buffer, or a stream

This error message usually occurs when you are performing some kind of data transformation or manipulation, and the result of that transformation is not one of the expected types: string, arraybuffer, buffer, or stream.

Let’s take a look at some examples to understand this error better:

Example 1: Invalid Data Type

    
const data = 123; // Invalid data type. Should be a string or an arraybuffer or a buffer or a stream

// Some transformation or manipulation on the data
const transformedData = data.toUpperCase(); // This transformation won't work since data is not of type string or arraybuffer or buffer or stream

In the above example, we are trying to convert the data to uppercase using the toUpperCase() method, which is applicable only to strings. Since the data is of type number (‘123’), which is not one of the expected types, it will throw the mentioned error.

Example 2: Incorrect Transformation Result

    
const data = "Hello, world!";

// Some transformation or manipulation on the data
const transformedData = {
  value: data,
  length: data.length
};

console.log(transformedData.toUpperCase()); // This transformation won't work since transformedData is not of type string or arraybuffer or buffer or stream

In this example, we are creating an object transformedData that holds the original value and length of the data. Then, we try to apply the toUpperCase() method directly on the object, which is not one of the expected types. Hence, it will result in the mentioned error.

Example 3: Valid Transformation Result

    
const data = "Hello, world!";

// Some transformation or manipulation on the data
const transformedData = data.toUpperCase(); // Valid transformation since data is a string

console.log(transformedData); // Output: "HELLO, WORLD!"

In this example, we are correctly transforming the data to uppercase since it is a string. Therefore, the transformation will be successful without any error.

To resolve the mentioned error, make sure you are performing the correct data transformation or manipulation based on the expected types mentioned in the error message.

Error: data after transformation must be a string, an arraybuffer, a buffer, or a stream