Testing support of Streams API

streams-test.html

<script>
    var setResult = setResult || function setResult(tag, bool) {
        console.log(tag + ' supported? ' + (bool ? 'yes' : 'no'));
    };

    // Basic support
    try {
        var result0 = true;

        // Test exposed globals
        result0 = result0 && ('ReadableStream' in window);
        result0 = result0 && ('ByteLengthQueuingStrategy' in window);
        result0 = result0 && ('CountQueuingStrategy' in window);

        // Test accessibility from fetch API
        if ('Response' in window) {
            result0 = result0 && (Object.getOwnPropertyNames(window.Response.prototype).indexOf('body') > -1);
        }

        // Test ReadableStreamDefaultReader
        result0 = result0 && Object.getPrototypeOf((new window.ReadableStream).getReader({ mode: undefined })).constructor.name === 'ReadableStreamDefaultReader';

        // Test ReadableStreamDefaultController
        new window.ReadableStream({
            start(controller) {
                result0 = result0 && Object.getPrototypeOf(controller).constructor.name === 'ReadableStreamDefaultController';
            }
        });

        setResult('streams0', result0);
    } catch (e) {
        setResult('streams0', false);
    }

    // Test WritableStream support
    try {
        var result1 = true;

        // Test exposed globals
        result1 = result1 && ('WritableStream' in window);

        setResult('streams1', result1);
    } catch (e) {
        setResult('streams1', false);
    }

    // Test pipeTo / pipeThrough support (note #2)
    try {
        var result2 = true;

        result2 = result2 && typeof window.ReadableStream.prototype.pipeThrough === 'function';
        result2 = result2 && typeof window.ReadableStream.prototype.pipeTo === 'function';
        
        const rs1 = new ReadableStream();
        rs1.pipeTo(new WritableStream());
        
        const rs2 = new ReadableStream();
        rs2.pipeThrough({ writable: new WritableStream(), readable: new ReadableStream() });

        setResult('streams2', result2);
    } catch (e) {
        setResult('streams2', false);
    }

    // Test BYOB support (note #3)
    try {
        var result3 = true;

        // Test ReadableByteStreamController
        var readableByteStreamCtrl = new window.ReadableStream({
            type: 'bytes',
            start(controller) {
                result3 = result3 && Object.getPrototypeOf(controller).constructor.name === 'ReadableByteStreamController';
            }
        });


        // Test ReadableStreamBYOBReader
        result3 = result3 && Object.getPrototypeOf(readableByteStreamCtrl.getReader({ mode: 'byob' })).constructor.name === 'ReadableStreamBYOBReader';

        setResult('streams3', result3);
    } catch (e) {
        setResult('streams3', false);
    }
</script>