1var xhr = new XMLHttpRequest();       
2    xhr.open("GET", "/path/to/local/image/file", true); 
3    xhr.responseType = "blob";
4    xhr.onload = function (e) {
5            console.log(this.response);
6            var reader = new FileReader();
7            reader.onload = function(event) {
8               var res = event.target.result;
9               console.log(res)
10            }
11            var file = this.response;
12            reader.readAsDataURL(file)
13    };
14    xhr.send()

1function getBase64Image(src, callback, outputFormat) {
2      const img = new Image();
3      img.crossOrigin = 'Anonymous';
4      img.onload = () => {
5        const canvas = document.createElement('canvas');
6        const ctx = canvas.getContext('2d');
7        let dataURL;
8        canvas.height = img.naturalHeight;
9        canvas.width = img.naturalWidth;
10        ctx.drawImage(img, 0, 0);
11        dataURL = canvas.toDataURL(outputFormat);
12        callback(dataURL);
13      };
14
15      img.src = src;
16      if (img.complete || img.complete === undefined) {
17        img.src = "data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==";
18        img.src = src;
19      }
20    }

1function encodeImageFileAsURL(element) {
2  var file = element.files[0];
3  var reader = new FileReader();
4  reader.onloadend = function() {
5    console.log('RESULT', reader.result)
6  }
7  reader.readAsDataURL(file);
8}
9<input type="file" onchange="encodeImageFileAsURL(this)" />