Solve Unexpected lexical declaration in case block. Error

Problem: Unexpected lexical declaration in case block . error was suddenly reported when writing code

Description: I suddenly reported Unexpected lexical declaration in case block. when I was writing code today. It was a bit boring at first. Later, I found that the type definition was written in the switch. The error code is as follows:

switch (item.value) {
    
    
	// 整理
	case RIGHT_MENU[0].value:
		const data = 1;	// 报错
		break;
	// 刷新
	case RIGHT_MENU[1].value:
		// 实现代码
		break;
	default:
		console.warn("未知菜单");
		break;
}

Solution:
This is an eslint error message, which means that a type declaration occurs unexpectedly in a case. Eslint does not allow variables to be declared in a case. It should be said that the declaration should be placed outside, and the case only performs assignments, such as:

let data=null;
switch (item.value) {
    
    
	// 整理
	case RIGHT_MENU[0].value:
		data = 1;	// 正确
		break;
	// 刷新
	case RIGHT_MENU[1].value:
		// 实现代码
		break;
	default:
		console.warn("未知菜单");
		break;
}