convert an image into Base64 string using JavaScript

function getBase64Image(src, callback, outputFormat) {
      const img = new Image();
      img.crossOrigin = 'Anonymous';
      img.onload = () => {
        const canvas = document.createElement('canvas');
        const ctx = canvas.getContext('2d');
        let dataURL;
        canvas.height = img.naturalHeight;
        canvas.width = img.naturalWidth;
        ctx.drawImage(img, 0, 0);
        dataURL = canvas.toDataURL(outputFormat);
        callback(dataURL);
      };

      img.src = src;
      if (img.complete || img.complete === undefined) {
        img.src = "data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==";
        img.src = src;
      }
    }