TransformStream: writable property

Available in workers

The writable read-only property of the TransformStream interface returns the WritableStream instance controlled by this TransformStream. This stream accepts input data that will be transformed and emitted to the readable stream.

Value

A WritableStream.

Examples

This example creates a TransformStream that converts all input text to uppercase letters. It writes some text to the writable stream, then reads the transformed text from the readable stream.

const stream = new TransformStream({
  transform(chunk, controller) {
    controller.enqueue(chunk.toUpperCase());
  },
});

// Write data to be transformed
const writer = stream.writable.getWriter();
writer.write("hello ");
writer.write("world");
writer.close();

// Read transformed data
const reader = stream.readable.getReader();
let done = false;
let output = "";
while (!done) {
  const result = await reader.read();
  if (result.value) {
    output += result.value;
  }
  done = result.done;
}
console.log(output); // HELLO WORLD

Specifications

Browser compatibility