from lwc download sobject attachment salesforce apex ligtning web component

downloadFile.js

downloadFile(){
    getPDF({
      filter:this.seachFilter
    })
      .then(result => {
        console.log(result);
        //check if no err
        if(!result.Error)
            this.saveFile( result);
        
      })
      .catch(error => {
        console.error('Error:', error);
    });
}
saveFile(file) {
    var link = document.createElement('a');
    link.innerHTML = 'Download PDF file';
    link.download = file.fileName;
    link.href = 'data:application/octet-stream;base64,' + file.Link;
    document.body.appendChild(link);
    link.click();
}

getAttachment.apex

@AuraEnabled
    public static Map<String, Object>  getAttachment(String contactId) {
        Map<String, Object> mapReturn= new Map<String, Object>();
        try {
            Attachment a=[select Name, Body, BodyLength from Attachment where ParentId = : contactId LIMIT 1];
            mapReturn.put('Link',EncodingUtil.base64Encode(a?.Body));
            mapReturn.put('fileName',a?.name);
        } catch (exception e) {
            mapReturn.put('Error',true);
            mapReturn.put('ErrorMsg',e.getMessage());
        }finally {
            return mapReturn;
    }
    }