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This article will explain in detail whether the declaration of javascript variables must use var. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

In javascript, var is not required for variable declaration, but let and const are also available. Use let to declare block-level scoped variables, syntax "let variable name;" or "let variable name = value;"; use const to declare variables that cannot modify data, syntax "const variable name = value;".

The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.

JavaScript is a weakly typed language and can be used directly without declaring variables. This is simple but not easy to find errors in variable names, so it is not recommended. It is common practice to declare the variable before using the JavaScript variable.

Currently, there are three ways to declare JavaScript variables, using the var, let, and const keywords.

Var, let, and const can all declare variables, but there are many differences between them.

Use var to declare variables with global or function-level scope.

Use let to declare variables that are scoped at the block level.

Variables declared using var and let can be changed while the script code is running. If you want the value of the variable to remain the same throughout the run of the script code, you need to use const to declare it.

The syntax for let to declare a variable:

Let variable name; let variable name 1, variable name 2, … , variable name 1 = value 1, variable name 2 = value 2,... , variable name n = value n

The syntax for const to declare a variable:

Const variable name = value

It is important to note that when you use const to declare a variable, you must assign an initial value to the variable, and that value cannot be modified during the entire run of the code. In addition, variables cannot be declared multiple times. Any failure to meet any of these requirements will lead to an error.

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