JAVA language changed to javascript

In recent years, with the rapid development of Internet technology, front-end Web development has become more and more important. In web development, JavaScript plays an inevitable and important role. However, for developers who are about to switch from back-end JAVA language to front-end development, it may be difficult to understand and learn JavaScript through JAVA language experience. This article will introduce how to use the thinking habits of the JAVA language to quickly master JavaScript.

First of all, what we need to understand is that JavaScript has many similarities with JAVA. Both are object-oriented programming languages ​​that are highly readable and maintainable. Therefore, when learning JavaScript, we can learn from the JAVA thinking model to quickly master the core concepts of JavaScript.

Variables and Types

Variables are very important for program development. In JAVA, we need to declare a variable before we can use it, and when declaring a variable we need to explicitly specify the data type. Similarly, in JavaScript, variables need to be declared first, but there is no need to explicitly specify the type of the variable, it will automatically determine and determine the type. For example, when declaring an integer variable in JAVA, you need to write:

int num = 10;

, while in JavaScript, you write it directly:

var num = 10;

In JavaScript, commonly used data types are similar to JAVA, including strings , numbers, Boolean types, arrays, etc. The difference mainly lies in the definition and use of types. Mastering the use of variables and type conversion is very necessary in the subsequent development process.

Objects and Classes

In JAVA, object-oriented programming is a very common and important concept. JavaScript also has the concepts of objects and classes, but it is slightly different from the JAVA language. There are no class definitions in JavaScript, but there are functions. Functions can be regarded as generators of objects and can be used to define the properties and methods of objects. In JAVA, objects need to be defined through classes. Properties and methods are part of the class, and objects are generated by instantiating the class.

In JavaScript, we can use the "function constructor" to define objects, for example:

function Person(name){
  this.name = name;
  this.sayHello = function(){
    console.log('Hello, ' + this.name);
  }
}

var person1 = new Person('Tom');
person1.sayHello(); // 输出 "Hello, Tom"

In JAVA, we need to define objects through classes, for example:

public class Person{
  String name;
  public Person(String name){
    this.name = name;
  }
  public void sayHello(){
    System.out.println("Hello, " + name);
  }
}

Person person1 = new Person("Tom");
person1.sayHello(); // 输出 "Hello, Tom"

Although it is a different way, it is essentially the same efficient implementation of object-oriented programming.

Control statements

In JAVA, common control statements include if statements, loop statements, switch statements, etc. These statements also exist in JavaScript and are used in a very similar way to JAVA. In JavaScript, you can also use if statements for judgment, and loop statements such as for, while, do-while for loop control, and if-else statements and switch-case statements are also similar to JAVA.

Function

Function is the core of JavaScript programming. Functions can not only be used as generators of objects, but can also be called as ordinary functions. In JAVA, functions can only be defined inside a class and called by instantiating the class. In JavaScript, functions can be defined and called directly. For example:

function add(a, b){
  return a + b;
}

var result = add(3, 4); // result = 7

In JAVA, you also need to define a method to implement addition operation, but the calling method is to call it after instantiating the class:

public class Adder{
  public int add(int a, int b){
    return a + b;
  }
}

Adder adder = new Adder();
int result = adder.add(3, 4); // result = 7

Summary

Through the above Comparing the JAVA and JavaScript languages, we can find that although the two have slightly different language mechanisms and syntax, their core ideas are similar. Learning from JAVA's thinking model will be helpful for learning JavaScript. In specific development, learning a language is just a process and is not limited to a certain language. When learning a new language or technology, it is important to understand its ideas and principles, find the correspondence with known technologies, and quickly master it with the help of existing experience.

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