What does javascript mean?

JavaScript is a programming language commonly used for web development, and is often used to implement dynamic effects, form validation, interactive functions, etc. Among them, it represents a very important concept and is a part that must be mastered in programming.

In JavaScript, it represents an object or function, which can be passed as a parameter to other functions, or assigned to a variable or property. Objects in JavaScript are basically composed of key-value pairs, so they are often called "key-value pairs" or "properties". "Key" is usually a string, indicating the name of the property in this object, and "value" can be any JavaScript data type, including numbers, strings, Boolean types, arrays, objects, etc.

A typical object definition is as follows:

var obj = {
  name: 'John',
  age: 30,
  skills: ['JavaScript', 'HTML', 'CSS'],
  address: {
    city: 'New York',
    street: 'Broadway'
  }
};

In this example, the object obj has four attributes: name, age , skills and address. The values ​​of name and age are string and numeric types respectively. The value of skills is an array containing three string elements. address The value of is an embedded object. We can obtain and modify these property values ​​in the following ways:

obj.name  // "John"
obj.age = 35;
obj.skills.push('React');
obj.address.city = 'Los Angeles';

In addition to ordinary objects, functions in JavaScript can also be assigned as a value to a variable or property. The definition of a function usually uses the function keyword:

function sayHello(name) {
  console.log('Hello, ' + name + '!');
}

You can use the () operator to execute the function:

sayHello('John');  // Hello, John!

In addition, since JavaScript The function is actually an object, so it can also be assigned to a variable or property, as shown below:

var func = function(name) {
  console.log('Hi, ' + name + '!');
};

obj.greet = func;
obj.greet('Sarah');  // Hi, Sarah!

In this example, we assign an anonymous function to the variable func, and then This function is used as an attribute of object obj, and finally this function is executed by accessing the attribute.

It should be noted that in JavaScript, we can access objects or functions through variable names. However, if this variable name does not define a corresponding object or function, JavaScript will throw a ReferenceError error. Therefore, when writing JavaScript code, we need to be careful about the naming and use of variables to avoid such errors.

In short, it represents a very important concept in JavaScript and is crucial for understanding JavaScript programming and developing web applications. I hope this article will be helpful to readers when learning JavaScript in depth.

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