How to check if the process was executed successfully in batch - batch-file

Question

I try to create a windows batch script that install nodeJs, express and bower, but for now doesn't work and I cant know what is the problem because the terminal closed after some seconds.
If I run all the instructions of the batch script one by one into a CMD all work OK.
How can I validate that every process was executed successfully? I mean if the install of express fail, get a message like "fail express framework install"
I think that the problem is the script doesn't wait finished install the fisrt block of code when try to install the next block.
Any idea for resolve?
This is my script:
::Windows Batch Script for Install nodeJs, express framework for nodeJs, bower and Ionic
#setlocal
#echo off
:: Install nodeJs & NPM
echo Instalando NodeJs ^& NPM (Node Package Manager)...
echo.
start /wait msiexec /i C:\EMWA\installers\node.msi /passive /norestart
::Install express framework
echo Instalando express framework nodejs
echo.
npm install express-generator -g
:: Install bower
echo Install bower
echo.
npm install -g bower
:: create a test project
IF NOT EXIST C:\EMWA\projects
mkdir C:\EMWA\projects
IF NOT EXIST C:\EMWA\projects\emwa_test
mkdir C:\EMWA\projects\emwa_test
pause > null

Answer 1

This is the purpose of the ERRORLEVEL keyword in the IF statement. See IF /? for details:
C:\...>if /?
Performs conditional processing in batch programs.
IF [NOT] ERRORLEVEL number command
....
NOT Specifies that Windows should carry out
the command only if the condition is false.
ERRORLEVEL number Specifies a true condition if the last program run
returned an exit code equal to or greater than the number
specified.
....
%ERRORLEVEL% will expand into a string representation of
the current value of ERRORLEVEL, provided that there is not already
an environment variable with the name ERRORLEVEL, in which case you
will get its value instead. After running a program, the following
illustrates ERRORLEVEL use:
goto answer%ERRORLEVEL%
:answer0
echo Program had return code 0
:answer1
echo Program had return code 1
You can also use numerical comparisons above:
IF %ERRORLEVEL% LEQ 1 goto okay
....
C:\...>
This works as long as the commands set an exit status, which many do.