Javascript - I created a blob from a string, how do I get the string back out?

In order to extract data from a Blob, you need a FileReader.

var reader = new FileReader();
reader.onload = function() {
    alert(reader.result);
}
reader.readAsText(blob);

@joey asked how to wrap @philipp's answer in a function, so here's a solution that does that in modern Javascript (thanks @Endless):

const text = await new Response(blob).text()