What should I do if the method of the javascript class does not execute?

JavaScript is an object-oriented programming language and supports classes and class-related methods. Therefore, when you write JavaScript code, you will often encounter various types of problems. One of the common problems is that class methods are not executed.

When you write methods of a JavaScript class, you need to make sure that you have correctly defined the class constructor and class instances. Otherwise, you may run into problems with class methods not executing. In this article, we will explore some common reasons why class methods do not execute and workarounds.

1. Object properties are not set correctly when defining the constructor of a class

In JavaScript, the constructor of a class is the process of creating a new object. Therefore, when you define a class, you must ensure that your constructor sets the object properties correctly, otherwise your methods may not execute correctly. For example, the following code defines a class, but does not correctly set an object property 'text':

class Message {
  constructor() {
    // 没有设置对象属性 'text'
  }

  showText() {
    console.log(this.text);
  }
}

let message = new Message();
message.showText(); // 无法执行：'this.text' 为undefined

The above code will cause an error because the 'text' property is not set in the constructor, causing the object The creation was unsuccessful, so the 'text' property cannot be accessed when executing the 'showText()' method. To fix this problem, you must set the properties correctly in the constructor:

class Message {
  constructor(text) {
    this.text = text;
  }

  showText() {
    console.log(this.text);
  }
}

let message = new Message('Hello, World!');
message.showText(); // 输出: 'Hello, World!'

2. Class instances are not created correctly

Another common reason for creating class instances is Incorrect way. You should use the 'new' keyword to create a new instance of a class. If you forget to use 'new', the new object will not be created and the object's methods will not be executed. For example:

class Person {
  constructor(name) {
    this.name = name;
  }

  sayHello() {
    console.log('Hello, my name is ' + this.name);
  }
}

let person = Person('John'); // 忘记使用 'new' 关键字
person.sayHello(); // 无法执行：'person' 不是一个对象

Be sure to use the 'new' keyword to create an instance of the class, otherwise the class method will not be executed. For example:

class Person {
  constructor(name) {
    this.name = name;
  }

  sayHello() {
    console.log('Hello, my name is ' + this.name);
  }
}

let person = new Person('John'); // 正确创建类的实例
person.sayHello(); // 输出: 'Hello, my name is John'

3. Wrong declared method name

When you define a method of a class, you should make sure that the method name is not spelled incorrectly. If the method name is misspelled, the method will not be successfully defined in the class and cannot be called. For example:

class Person {
  constructor(name) {
    this.name = name;
  }

  sayHello() {
    console.log('Hello, my name is' + this.name);
  }

  spesak() {
    console.log('I am speaking.'); // 拼写错误，应该是 'speak'
  }
}

let person = new Person('John'); 
person.speak(); // 无法执行：拼写错误的方法名称

To solve this problem, you need to double-check your code for typos and fix them.

Conclusion

It is a common problem that class methods do not execute, usually because the object properties are not set correctly in the class constructor, the class instance is not created correctly, or the method name is spelled incorrectly. This problem can be solved by carefully checking the code to ensure that the class and its instances are created correctly, the way the class is defined.

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