Nodejs Promises unusual behaviour with exec - node.js

Question

i am executing the following code in nodejs and want an output like this :
and want an output like this
Running Code
Compiling Code
Executing Code
Done Execution
Done Compiling
Done everything
But the output is like this :
Running Code
Compiling Code
Executing Code
Done Execution
Done Compiling
Done everything
This is a strange behaviour :/
var sys = require('sys');
var exec = require('child_process').exec;
var Q = require('q');
var script_sh = 'bash -c' + ' "echo "hegr" ;"';
function compile(req, res) {
var deferred = Q.defer();
console.log('Compiling Code');
exec(script_sh, function puts(err, stdout, stderr) {
if (err || stderr) {
console.log('Error While Compiling');
console.log(err);
res.send(stderr || err );
return deferred.reject(err);
}
console.log('Done Compiling');
return deferred.resolve();
});
return deferred.promise;
}
function execute(req, res) {
console.log('Executing Code');
var deferred = Q.defer();
exec(script_sh, function puts(err, stdout, stderr) {
if (err || stderr) {
console.log('Error While Execution');
console.log(err || stderr);
res.send(err);
return deferred.reject(err || stderr);
}
console.log('Done Execution');
return deferred.resolve();
});
return deferred.promise;
}
function run_code(req,res) {
console.log('Running Code');
compile(req,res)
.then(execute(req,res))
.then(function() {
console.log('Done everything');
}).fail(function (error) {
error.status = 412;
return ;
});
};
module.exports = run_code;
(function() {
if (require.main == module) {
var req = console.log;
var res = console.log;
res.send = console.log;
run_code(req,res);
}
}());

Answer 1

You're not waiting for compile to resolve before invoking execute, but rather using the return value of execute as an argument to then, which happens to be a resolved Promise;
compile(req,res)
.then(execute(req,res))
The argument to then is evaluated when the body of the function run_code is evaluated, not when compile resolves. To wait for compile to resolve before executing execute, use:
compile(req, res)
.then(execute.bind(null, req, res));
execute.bind(null, req, res) will return a pre-bound function that will execute after compile resolves.
Alternatively,
compile(req, res)
.then(function () {
return execute(req, res);
});