Hello everyone, this is the table of contents of my speech today, divided into Java, JavaScript, ABAP three programming languages to tell.

Java

•JAD • Javap •Java Decompiler •Source Monitor •Visual VM •Refactor Menu in Eclipse

ABAP

JavaScript

•ESLint for Fiori Apps

•Check Jenkins build log

•JSlint for Sublime Text 2

•Code check in WebIDE

•Profile in Chrome

Is it correct to introduce a Boolean parameter control method behavior into a method?

package one;
public interface Constants {
  String NAME = "Sun Wukong";
  int BP = 10000;
}
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package two;

public class Constants {
   public static final String NAME = Vegeta;
   public static final int BP = 9000;
}
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String[] array = { "Steve Jobs"."Zhang Xiaolong" };
List list = Arrays.asList( array );

System.out.println( list );
// Print out [Steve Jobs, Zhang Xiaolong]
System.out.println( array );
// -> [Ljava.lang.String;@6f548414

list.equals( Arrays.asList( "Steve Jobs"."Zhang Xiaolong"))// -> true
array.equals( new String[] { "Steve Jobs"."Zhang Xiaolong"})// -> false
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Number[] numbers = new Integer[10];
numbers[0] = Long.valueOf( 0 ); 
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Interesting commas in Javascript

function a() {
  console.log("I was called!");
  return "Jerry";
}
var b = a(), a;
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Then execute the following code:

console.log(b);
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It prints out Jerry

Look at this code again:

var d = (function c(){
  returna(),a; }) ();console.log(d);
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Will print:

I was called!
function a() {
  console.log("I was called!");
  return "Jerry";
}
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What about this code?

(function() {
    var e = f = 1; }) ();Copy the code

Uncaught ReferenceError: f is not defined

Interesting semicolons in JavaScript

var b = function(para) {
  return {
  doSomething: function() {
  console.log("hello: " + para);
  returnpara; }}}var a = 1, x = 3, y = 4, s
s = a + b
(x + y).doSomething() // Print hello: 7
console.log(s) // Print out 8
function test(i){
  var result = i++;
  return
  result
}
console.log("test: " + test(3)) // Print undefined
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Let’s go ahead and look at this code

s = function(x){ console.log("called: " + x ); return x}
(1 + 2).toString()

s = function(x){ console.log("called: " + x ); return x}(1 + 2).toString()

// Print called: 3
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Tip – How do you embed your own enhanced logic into Legacy code

var bigFunction = function() {
      // big logic
      console.log("big logic"); // This sentence simulates how we embed our new logic in a very long piece of legacy code
}

// The following solution is elegant and does not directly modify the legacy function itself
var _old = bigFunction;
bigFunction = function() {
    if ( _old ) {
         _old();
    }
    console.log("our own enhancement");
}
bigFunction();

// The third solution uses slice-oriented programming ideas and is more advanced
var bigFunction = function() {
  // big logic
  console.log("big logic");
}
bigFunction = ( bigFunction || function() {} ).after( function() {
     console.log("our own logic");
});
bigFunction();
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How to elegantly add utility code for performance test statistics to a function

var append_doms = function() {
    var d = new Date(a);// dirty code - nothing to do with application logic!!!
    for( var i = 0; i < 100000; i++) {
      var div = document.createElement( "div");
        document.body.appendChild(div);
    }
    // dirty code - nothing to do with application logic!!!
    console.log(" time consumed: " + ( new Date() - d));
};
function test() {
  append_doms();
}
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Traditional solution: the implementation is ugly by forcing red standard tool code for collecting performance tests into a function body full of business logic:

Let’s look at a solution that takes a slice-oriented Programming approach: AOP-aspect Oriented Programming

var append_doms = function() {
    for( var i = 0; i < 100000; i++) {
      var div = document.createElement( "div");
        document.body.appendChild(div); }};var log_time = function( func, log_name) {
       return func = ( function() {
           var d;
           return func.before( function(){
                 d = new Date(a); }).after(function(){
                 console.log( log_name + ( new Date() - d)); }); }) (); };function test() {
 log_time(append_doms, "consumed time: ") (); }Copy the code

How do I avoid a lot of if-else checking in my code

Before calling the real OData API, the system has a large number of IF ELSE checks the API’s input betelgeuse:

var send = function() {
     var value = input.value;
     if( value.length === ' ' ) {
           return false;
     }
     else if( value.length > MAX_LENGTH) {
           return false; }...// lots of else
     else {
        // call OData API}}Copy the code

A more elegant solution:

Encapsulate these different check rules in JavaScript functions as properties of a rule object:

var valid_rules = {
      not_empty: function( value ) {
         returnvalue.length ! = =' ';
      },
      max_length: function( value ) {
         returnvalue.length <= MAX_LENGTH ; }}Copy the code

Implement a new check function that checks the properties of an object and performs the check logic:

var valid_check = function() {
     for( var i in valid_rules ) {
          if ( vali_rules[i].apply( this.arguments) = = =false ) {
                return false; }}}Copy the code

OData calls are now very elegant:

var send = function( value ) {
       if ( valid_check( value ) === false ) {
             return;
       }
      // call OData API
}
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That eliminates the IF ELSE.

Another way to eliminate the IF ELSE branch through the design pattern of the Chain of Responsibility code refactoring:

Let’s look at the traditional implementation:

// Priority: ActiveX > HTML5 > Flash > Form(default)
function isActiveXSupported(){
  / /...
  return false;
}
function isHTML5Supported(){
  / /...
  return false;
}
function isFlashSupported(){
  / /...
  return false;
}
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A lot of if-else:

var uploadAPI;
if ( isActiveXSupported()) {
  // lots of initialization work
  uploadAPI = { "name": "ActiveX"};
}
else if( isHTML5Supported()) {
  // lots of initialization work
  uploadAPI = { "name": "HTML5"};
}
else if( isFlashSupported()) {
  // lots of initialization work
  uploadAPI = { "name": "Flash"};
}
else {
  // lots of initialization work
  uploadAPI = { "name": "Form"};
}
console.log(uploadAPI);
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Look again at the realization of the responsibility chain design pattern:

Chain of Responsibility

var getActiveX = function() {
  try {
  // lots of initialization work
  return { "name": "ActiveX"};
  }
  catch (e) {
  return null; }}var getHTML5 = function() {
  try {
  // lots of initialization work
  return { "name": "HTML5"};
  }
  catch (e) {
  return null; }}Copy the code

var uploadAPI = getActiveX.after(getHTML5).after(getFlash).after(getForm)();
console.log(uploadAPI);
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The String in the Java

public class stringTest {
public static void main(String[] args) {
  String userName = "Jerry";
  String skill = "JS";
  String job = "Developer";
  Stringinfo = userName + skill + job; System.out.println(info); }}Copy the code

Use Javap to decompile the Hello World program above to learn:

For more of Jerry’s original articles, please follow the public account “Wang Zixi “: