javascript - How to turn this getImageData into a promise? -

the following function takes , image url, loads it, , returns width , height:

function getimagedata (url) {   const img = new image()   img.addeventlistener('load', function () {     return { width: this.naturalwidth, height: this.naturalheight }   })   img.src = url } 

the problem is, if this:

ready () {   console.log(getimagedata(this.url)) } 

i undefined because function runs imaged hasn't loaded yet.

how use await/async (or new promise) return value when photo has loaded , width , height available?

how use async/await turn callback function promise?

you don't. as usual, use new promise constructor. there's no syntactic sugar that.

function loadimage(url) {   return new promise((resolve, reject) => {     const img = new image();     img.addeventlistener('load', () => resolve(img));     img.addeventlistener('error', reject); // don't forget 1     img.src = url;   }); } 

how use await/async log value when photo has loaded , width , height available?

you can do

async function getimagedata(url) {   const img = await loadimage(url);   return { width: img.naturalwidth, height: img.naturalheight }; } async function ready() {   console.log(await getimagedata(this.url)) }