node.js - How to handle asynchronous callbacks within an if - else statement? -

for project need alter values in file in 5 if-statements executed 1 after another, , after things done, need save file. 1 of alteration contains asynchronous save image function. problem i'm having that function has not finished time program gets file writing. how should handle callbacks within if-statement? save image function should executed before program proceeds next if statement.

if(criterium1){... //alter file}  if(criterium2){     saveimage(searchvalue, folder,callback(error)){         ... //alter file     } if(criterium3){... //alter file}  fs.writefile(opffile, xml, function(error) {     callback(null);  });   var saveimage = function(searchvalue, folder, callback){     var images = require ('google-images2');     images.search(searchvalue, function(error, image){         callback(null);     });  }; 

can give me pointer on how handle this? thanks! kind regards, eva

you can use async library, series control flow. https://caolan.github.io/async/docs.html#series

you want execute if statements tasks in array (first argument). make sure call callback when asynchronous actions done. second argument callback execute when tasks done.

async.series([     function(callback){         if(criterium1) {           //alter file           // make sure call callback         } else {           callback(null, null);         }     },     function(callback){         if(criterium2) {           //alter file           // make sure call callback           // looks can pass callback saveimage function         } else {           callback(null, null);         }     } ], function () {   fs.writefile(opffile, xml, function(error) {     callback(null);  }); });