How to delete const in javascript

Javascript is a flexible programming language that allows developers to declare variables in code using keywords such as const, let, and var. Among them, the const keyword is used to define a constant, that is, a variable that once defined cannot be changed. In some cases, we may need to delete or modify const type variables, but is this possible? If so, how should we handle it? This article explores these issues.

1. What is a const variable?
In Javascript, a variable declared using const means that its value cannot be changed once assigned. For example:

const a = 10;
a = 20; //会抛出TypeError异常

Since the value of a const variable cannot be changed, when writing code, we usually initialize it while declaring the const variable. At the same time, const variables are usually designed to protect values ​​in the code that should not be changed, such as mathematical constants, API keys, etc.

2. Methods of deleting const variables
Deleting const variables seems like an impossible task, because the value of a const variable cannot be changed, let alone deleted. However, there are actually two ways to get around this limitation.

1. Use object attributes to modify const variables
Although const variables cannot be modified directly, if it is an attribute of an object, then the value of the const variable can be modified indirectly by modifying the object. For example:

const obj = {a:10};
obj.a = 20;
console.log(obj.a); //20

In the above code, we first declare a const type variable obj and initialize it to an object containing the a property. Although obj is a constant, the a attribute is not restricted. Next, we indirectly modified the value of the const variable by modifying the value of the a attribute of the obj object.

2. Use variable redeclaration
We can use another variable to redeclare a const variable. For example:

const a = 10;
{
  const a = 20;
  console.log(a); //20
}
console.log(a); //10

In this example, we first declare a const variable named a and initialize it to 10. Next, we declare another const variable named a within a code block (wrapped by curly braces) and initialize it to 20. Since this code block is a new scope, variable a will not affect the a variable defined in the outer scope.

3. Avoid deleting const variables
We already know how to delete const variables, but this does not mean that we should use this technique often in our code. In fact, a const variable is designed to be a constant, which means that its value should remain unchanged throughout the run of the program. If we need to modify a const variable, it indicates that we may not have taken into account the required flexibility when defining the variable, which may lead to errors and confusion in the code.

Also, const variables are considered very optimized because the compiler can optimize based on the type and usage of the variable. If we modify or delete const variables, it may affect the optimization effect of the compiler, resulting in lower performance of the code.

To sum up, we should avoid deleting const variables as much as possible. If we really need to modify the value of a variable, consider using the let keyword to define the variable so that we can easily change the value of the variable when needed.

4. Conclusion
Although we can delete const variables through some techniques, this is not a recommended approach. Const variables are designed to be constants and should remain unchanged while the program is running. If we need to use mutable values ​​while writing code, we should use the let keyword to declare the variable and change the value of the variable when needed. Only in rare cases should you use indirect modification or redeclaration of const variables.

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