// html
// <input type="file" onchange="imagesSelected"  multiple accept=".gif,.jpg,.jpeg,.png" />

async function imagesSelected(event) {
		let files = [...event.target.files];
		let images = await Promise.all(files.map(f=>{return readAsDataURL(f)}));
    //all images' base64encoded data will be available as array in images
}

function readAsDataURL(file) {
		return new Promise((resolve, reject)=>{
			let fileReader = new FileReader();
			fileReader.onload = function(){
				return resolve({data:fileReader.result, name:file.name, size: file.size, type: file.type});
			}
			fileReader.readAsDataURL(file);
		})
}