Case Analysis of const keyword

In this article, the editor introduces "const keyword case analysis" in detail, with detailed content, clear steps and proper handling of details. I hope this "const keyword case analysis" article can help you solve your doubts.

Const keyword

Const is used to declare one or more constants. The declaration must be initialized, and the value cannot be modified after initialization:

Case study

Const PI = 3.141592653589793

PI = 3.14; / / error report

PI = PI + 10; / / error report

Const defines constants similar to variables defined using let:

Both are block-level scope

Cannot have the same name as any other variable or function in its scope

There are two other differences between the two:

Constants declared by const must be initialized, while variables declared by let do not

The value of the const definition constant cannot be modified by re-assignment, nor can it be declared again. The value of the variable defined by let can be modified.

Var x = 10

/ / the output x here is 10

{

Const x = 2

/ / the output x here is 2.

}

/ / the output x here is 10

Constants declared by const must be initialized:

/ / incorrect writing

Const PI

PI = 3.14159265359

/ / correct writing

Const PI = 3.14159265359

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