Question

22

access blob value outside of canvas.ToBlob() async function

rated 0 times [ 24] [ 2] / answers: 1 / hits: 16135 / 7 Years ago, sat, february 25, 2017, 12:00:00

I'm working with HTMLCanvas element that return the blob object outside of the async toBlob() function. This function doesn't return an output value, so I'm trying to declare a variable outside and access it through the command.

How I can use JS Promise for this scenario?

var myblob;

            canvas.toBlob(function(blob) {                         

                              myblob = blob;

                              console.log(inside  + myblob); // getting value after the console outside

                           })

 console.log( outside  + myblob); // getting undefined

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ryderalfonsos

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answered 7 Years ago isaac · Accepted Answer

You can use Promise constructor, pass Blob instance to resolve(), access Promise value at .then()

function getCanvasBlob(canvas) {

  return new Promise(function(resolve, reject) {

    canvas.toBlob(function(blob) {

      resolve(blob)

    })

  })

}



var canvasBlob = getCanvasBlob(canvas);



canvasBlob.then(function(blob) {

  // do stuff with blob

}, function(err) {

  console.log(err)

});