Base64转Blob或者File，arrbuffer和Blob

Base64转Blob或者File

changeBase64ToFileOrBlob(base64String, type = "file") {
      let arr = base64String.split(",");
      let mime = arr[0].match(/:(.*?);/)[1]; // 此处得到的为文件类型
      let bstr = atob(arr[1]); // 此处将base64解码
      let n = bstr.length;
      let u8arr = new Uint8Array(n);
      while (n--) {
        u8arr[n] = bstr.charCodeAt(n);
      }
      if (type === "blob") {
        let blob = new Blob([u8arr], { type: mime });
        return blob;
      } else {
        // 通过以下方式将以上变量生成文件对象，三个参数分别为文件内容、文件名、文件类型
        let file = new File([u8arr], "filename", { type: mime });
        return file;
      }
    },

ArrayBuffer转base64

 function arrayBufferToBase64(buffer) {
     var binary = '';
     var bytes = new Uint8Array(buffer);
     var len = bytes.byteLength;
     for (var i = 0; i < len; i++) {
         binary += String.fromCharCode(bytes[i]);
     }
     return window.btoa(binary);
 }

Blob转Base64

export function blobToBase64 (blob) {
    return new Promise((resolve, reject) => {
        const fileReader = new FileReader()
        fileReader.onload = (e) => {
            resolve(e.target.result)
        }
        // readAsDataURL
        fileReader.readAsDataURL(blob)
        fileReader.onerror = () => {
            reject(new Error('blobToBase64 error'))
        }
    })
}