Can't javascript change data?

Javascript is a very popular programming language that is widely used in web development, game development, desktop applications, etc. It is loved by many developers due to its flexibility and ease of use. However, although Javascript is very powerful, the common misconception that it cannot change data persists. This article will clarify this issue. Before that, it needs to be clear that Javascript can actually change data.

One of the most common tasks in Javascript is to modify the properties of an object or the elements of an array. Like other programming languages, Javascript has the ability to make modifications to data, providing developers with some very useful tools and features. For example, in Javascript, we can modify data encapsulated in an object or array using the following methods:

Modification of object properties: You can use the dot syntax or square bracket syntax of the object.

Example:

var obj = {name: "Tom", age: 18};
obj.name = "Jack";
console.log(obj); //输出：{name: "Jack", age: 18}

obj["age"] = 20;
console.log(obj); //输出：{name: "Jack", age: 20}

Modification of array elements: You can use the subscript of the array

Example:

var arr = [1, 2, 3, 4, 5];
arr[2] = 100;
console.log(arr); //输出：[1, 2, 100, 4, 5]

In addition to objects and arrays, Javascript also There are many other data structures and variable types that can also be modified and used, such as strings, numbers, booleans, functions, and more. However, changing the value of a primitive data type is not allowed in Javascript, for example:

var num = 10;
num += 5;
console.log(num); // 输出15

// 但是以下赋值会报错：
num = 20; // TypeError: Assignment to constant variable.

This is because Javascript variables have different data types, including primitive data types and object data types. Primitive data types include numbers, strings, Boolean, null, and undefined values, while object data types include objects, arrays, functions, and more. Primitive data types are stored on the stack, while object data types are stored on the heap. This difference also causes errors when modifications are made to primitive data types because they are stored on the stack, which does not support modifications.

Although Javascript cannot directly modify the value of the original data type, we can still change the value of the original data type in the program by reassigning the variable. For variables of object data type, we can directly modify their properties or element values ​​to change their values.

In programming, modification of data is very important. In many scenarios, we need to update and change data at any time. In order to develop better using Javascript, we must understand the differences between Javascript's data types and variable types and use them in the correct context.

Summary:

Javascript can change the data by modifying the properties of the object or the elements of the array, but it cannot directly modify the value of the original data type. Developers should be aware of this when using Javascript and make modifications to data in the appropriate context. Understanding this can ensure that developers can use Javascript more efficiently.

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