1.图片路径转64 

function imageUrlToBase64(url) {
  let homeImage = new Image(); 
  // 解决跨域问题 
  homeImage.setAttribute("crossOrigin", "anonymous");
  homeImage.src = url;
  //homeImage.onload为异步加载
  homeImage.onload = () => {
    let canvas = document.createElement("canvas");
    canvas.width = homeImage.width;
    canvas.height = homeImage.height;
    let context = canvas.getContext("2d");
    context.drawImage(homeImage, 0, 0, homeImage.width, homeImage.height);
    let quality = 0.8;
    // 这里的dataurl就是base64类型
    let dataURL = canvas.toDataURL("image/jpeg", quality);
    console.log(dataURL);
    // base64ToFile(dataURL, "moren"); // 这里是将base64转为file格式的方法
  };
}

1.1图片转file

function imageToBase64(homeImage) {
    let canvas = document.createElement("canvas");
    canvas.width = homeImage.width;
    canvas.height = homeImage.height;
    let ctx = canvas.getContext("2d");
    ctx.drawImage(homeImage, 0, 0, homeImage.width, homeImage.height);
    let ext = img.src.substring(homeImage.src.lastIndexOf(".") + 1).toLowerCase();
    let dataURL = canvas.toDataURL("image/jpeg" + ext);
    console.log(dataURL);
    return dataURL;
};

2.base64转file 

function base64ToFile(base64, fileName) {
  let arr = base64.split(",");
  let mime = arr[0].match(/:(.*?);/)[1];
  let bytes = atob(arr[1]);
  let n = bytes.length;
  let ia = new Uint8Array(n);
  while (n--) {
    ia[n] = bytes.charCodeAt(n);
  }
  return new File([ia], fileName, { type: mime });  // 将值抛出去
}

3.file转base64

function getBase64(file) {
  // 直接将处理结果返回
  return new Promise((resolve, reject) => {
    let reader = new FileReader();
    let fileResult = "";
    reader.readAsDataURL(file);
    reader.onload = () => {
      fileResult = reader.result.toString();
    };
    reader.onerror = (error) => {
      reject(error);
    };
    reader.onloadend = () => {
      resolve(fileResult);
    };
  });
}