function base64ToArrayBuffer(base64) {

    let binaryString = window.atob(base64);

    let binaryLength = binaryString.length;

    let bytes = new Uint8Array(binaryLength);

​

    for (let i = 0; i < binaryLength; i++) {

        let ascii = binaryString.charCodeAt(i);

        bytes[i] = ascii;

    }

    return bytes;

}

arrayBufferToBase64(Arraybuffer, Filetype, fileName) {

        let binary = '';

        const bytes = new Uint8Array(Arraybuffer);

        const len = bytes.byteLength;

        for (let i = 0; i < len; i++) {

          binary += String.fromCharCode(bytes[i]);

        }

        const file = window.btoa(binary);

        const mimType = Filetype === 'pdf' ? 'application/pdf' : Filetype === 'xlsx' ? 'application/xlsx' :

          Filetype === 'pptx' ? 'application/pptx' : Filetype === 'csv' ? 'application/csv' : Filetype === 'docx' ? 'application/docx' :

            Filetype === 'jpg' ? 'application/jpg' : Filetype === 'png' ? 'application/png' : '';

        const url = `data:${mimType};base64,` + file;

        // url for the file

        this.fileUrl = this.sanitizer.bypassSecurityTrustResourceUrl(url);

        // download the file

          const a = document.createElement('a');

          a.href = url;

          a.download = fileName;

          document.body.appendChild(a);

          a.click();

          document.body.removeChild(a);

          window.URL.revokeObjectURL(url);

      }