Node. js 4. Basics

 

Encoding:

Node. jsSupportedUTF-8 ("utf8 "),ASCII ("ASCII ")AndBinary ("binary ")Encoding, relatively speaking,ASCIIAndBinaryIt will be faster,UTF-8It will be much slower and should be avoided as much as possible.

 

Globals

Arguments:

VaRSys = require ('sys '),
Some_argument = process. argv [2];

//Argument example

If(! Some_argument ){
ReturnSYS. Puts ('usage: node' + _ filename. Replace (_ dirname + '/', '') + 'some _ argument ');
}

 
//Require example
SYS. Puts ('default require paths: '+ require. paths );

SYS. Puts ('adding current directory to require. Paths ');

Require. paths. unshift (_ dirname );

SYS. Puts ('modfied require. paths: '+ require. paths );
 

 

 

Run

 

Node global. js test_arg

The following information is output:

Adding current directory to require. Paths

Modified require. paths:/home/sinsay/projects/nodejs_example/4. bacics/global. JS,/home/sinsay /. node_modules,/home/sinsay /. node_libraries,/usr/local/lib/node

Sinsay @ Ubuntu :~ /Projects/nodejs_example/4. bacics $ node global. js

 

Process. argvThe command line parameters are saved. In the current example,Argv [0]IsNode, argv [1]IsGlobal. JS,

Argv [2]ParameterSome_argument

If(! Some_argument ){
ReturnSYS. Puts ('usage: node' + _ filename. Replace (_ dirname + '/', '') + 'some _ argument ');
}

 

 

If no parameters are provided during execution, the current script will output the correct method of using the script. And aboveCodeMedium,_ FilenameIs a global variable, which indicates the path of the currently executed file,

And he replaced_ FilenamePath in(_ DirnameIt is also a global variable, indicatingCurrent path)Only the file name is retained.

 

Require

Require. Paths

ProvidedRequireFindPackageOr other things, the path can be usedUnshiftTo add your directory for the search path, like:

Require. paths. unshift (_ dirname );

 

Process

ProcessThe object provides us with information about the current process, such as the processID,Running platform,Memory usage, etc....

You can also provide the exit status code when exiting the script,E. g:

 

Process. Exit (0 );

 

By default, the exit status code is0See the example below.

 

VaR Sys = require ('sys ');

//Dis play all command line arguments
SYS. Puts ('provided arguments :');
For(VaRKeyInProcess. ARGs ){
SYS. Puts (Key + ':' + process. argv [Key]);
}

//Process details (PID, platform, memory usage)
SYS. Puts ('\ npid:' + process. PID );
SYS. Puts ('Platform: '+ process. Platform );
SYS. Puts ('memory usage: '+ process. memoryusage (). RSS );

//Display User Environment
SYS. Puts ('\ nuser environment :');
For(VaRKeyInProcess. env ){
SYS. Puts (Key + ':' + process. env [Key]);
}

//Process exit code-default success code 0
Process. Exit (0 );

 

System Module

SystemThe module provides many ways for us to output information to the console.

 

SYS. Puts () // Output Information and line feed

SYS. Print () // Output information without line feed

SYS. debug ('some debug output ');

// Output Information and add the debug information. e. g:

// Debug: Some debug output

System. Log ('some log output ');
// Output Information, and add the current date and time, e. g:
// 20 Mar 23:17:15-some log output

SYS. Inspect (process. memoryusage ())
// Output information according to the rendering form of the object, e. g:
// {RSS: 5263360
// . Vsize: 41353216
// , Heaptotal: 2176512
// , Heapused: 963872
// }

The following is a sample script.:

VaR Sys = require ('sys ');

//Sys output examples
SYS. Puts ('output with Trailing newline ');
SYS. Print ('output ');
SYS. Print ('new line ');
SYS. Puts ('\ nadd new line to beginning and extra one at the end. \ n ');
SYS. debug ('some debug output ');
SYS. Log ('some log output ');

//Simple SYS. Inspect example
VaRProcess_memory = process. memoryusage ();
SYS. Puts ('\ nprocess. memoryusage ():');
SYS. Puts (SYS. Inspect (process_memory ));

 

 

Timers

 

You canNodeOfProgramUsed inJavascriptOfTimer, suchSetTimeout (), cleartimeout (), setinterval (), clearinterval (). Example:

VaRSys = require ('sys ');

//Simple timeout exapmle
VaRStart_time =NewDate ();
SYS. Puts ('string 2 second timer ');

SetTimeout (Function(){
VaREnd_time =NewDate ();
VaRDifference = end_time.gettime ()-start_time.gettime ();
SYS. Puts ('stopped timer after: '+
Math. Round (difference/1000) + 'seconds ');

Cleartimeout_example ();
},2000 );

function cleartimeout_example () {
var start_time = New date ();
sys. puts ('\ nstarting 30 second timer and stopping it immediately without triggering callback');

var timeout = setTimeout ( function () {
var end_time = New date ();
var difference = end_time.gettime () -start_time.gettime ();
sys. puts ('stoped timer after '+ math. round (difference/1000) + 'seconds');
}, 3000);
cleartimeout (timeout);
interval_example ();
}

FunctionInterval_example (){
VaRStart_time =NewDate ();
SYS. Puts ('\ nstring 2 second interval, stopped after 5th tick ');

VaR Count = 1;
VaR Interval = setinterval ( Function (){
If (COUNT = 5) clearinterval ( This );
VaR End_time = New Date ();
VaR Diffrence = end_time.gettime ()-
Start_time.gettime ();
SYS. Puts ('tick No. '+ Count + 'after' + math. Round (diffrence/1000) + 'second ');
Count ++;
},2000 );
}