file 文件与 base64 互相转化

base64转blob

const base64ToBlob = function(base64Data) {
	let arr = base64Data.split(','),
		fileType = arr[0].match(/:(.*?);/)[1],
		bstr = atob(arr[1]),
		l = bstr.length,
		u8Arr = new Uint8Array(l);
		
	while (l--) {
		u8Arr[l] = bstr.charCodeAt(l);
	}
	return new Blob([u8Arr], {
		type: fileType
	});
};

base64 转 file

function dataURLtoFile(dataurl, filename) {
	var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],
		bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
	while (n--) {
		u8arr[n] = bstr.charCodeAt(n);
	}
	return new File([u8arr], filename, { type: mime });
}	

file 转 base64

$(".myUpload").change(function(){
	var imgFile = this.files[0]; 
	//异步读取文件
	var reader = new FileReader();
	// 调用reader.readAsDataURL()方法，把图片转成base64
	reader.readAsDataURL(imgFile);
	reader.onload = function(evt) {
		var imgBase64Data = evt.target.result;
		
		//base64数据去头
		var head = imgBase64Data.indexOf("4") + 2;
		var base64Data = imgBase64Data.substring(head, imgBase64Data.length - head);
	}
}