Nodejs>------->> Chapter III: node. JS Basics

Chapter III: The basic knowledge of node. js

One: Console 1:console.log, Console.info Method in node. js

  1 console.log ("This isa test string.");

  1 node app1.js 1> info.log

1Console.log ("This is a test String.");2 3 //Start with the second argument and output all the strings sequentially4Console.log ("%s"，"Hoge","Foo");//output is Hoge foo5 //Convert object to string after output6Console.log ("%s","Hoge", {foo:"FOO"});//Output result is Hoge ({foo:foo})7 //Converts a value to a string output, starting with the second argument, outputting all values sequentially8Console.log ("%d", 10,12,14,15,15.5);//Output result is 10,12,14,15,15.59 //Convert string as numeric value, Output NanTenConsole.log ("%d","Hoge");//Output Nan One //Output percent sign AConsole.log ("%%","Hoge");//output% Hoge

1Console.log (" the");//using operator, output is 42Console.log (2/0);//Output Infinity3 4 varA=1;5 varb=2;6 //calculation of the value variable A + value variable b results in output7Console.log (A+B);//Output result is 38 After converting a numeric variable A to a string, use the + operation symbol to concatenate 2 strings after the output9Console.log (A.toString() +b.toString());//output result isTen  One varA=1; A vard=t; -Console.log (A==B);//Use comparison operator, output false -Console.log (a==1&&b==2);//Use logical operator, output true

2:console.error, Console.warn method

App1.js

  1  console.error ("This isanerror  ");

The result of the operation is:

  1 node app1.js 2> error.log

  1 node script.js 2> error.log

1module.js:4712     ThrowErr3^4 5Error:cannotFindModule ' i:\ Learning materials \node.js authoritative guide \ Source code \chapter3\ codes List 3-1\script.js '6AtFunction. Module._resolvefilename (module.js:469:15)7AtFunction. Module._load (MODULE.JS:417:25)8At Module.runmain (module.js:604:10)9At Run (bootstrap_node.js:389:7)TenAt startup (Bootstrap_node.js:149:9) OneAt Bootstrap_node.js:502:3 A 

3:console.dir method

Nodejs>------->> Chapter III: node. JS Basics