js try...catch statement essay-error prompts three consecutive try...catch

The function of try...catch is to catch errors, regardless of system errors or custom errors (throw)

try…catch-JavaScript | MDN
try…catch statement marks the block of statements to be tried and specifies a response that is thrown when an exception occurs

try…catch[…finally] is used as follows

try {
    
    
	// 被执行的语句

	// 被执行的语句中触发了报错
	throw "报错信息"
} catch(error) {
    
    
	// error 返回的报错信息

	// 如果在try块里有异常被抛出时执行的语句
	// 没有错误则不会执行
	console.log(error)
} finally {
    
    
	// 在try语句块之后执行的语句块。无论是否有异常抛出或捕获这些语句都将执行
	console.log("finally")
}

try…catch[…finally] can be a nesting doll (one layer of try…catch, one layer of try…catch, one layer of try…catch), the nearest catch will be found if an error is reported

If a value is returned from the finally block, then this value will become the return value of the entire try-catch-finally, regardless of whether there is a return statement in the try and catch. This includes exceptions thrown in the catch block.
For example, the entire try is in a function, and the return information of the finally can be used as the return information of the function.

function fun() {
    
    
	try {
    
    
		throw "报错信息"
	} catch(error) {
    
    
		console.log(error)
	} finally {
    
    
		return "finally.return 相当于上一级的 return"
	}
	console.log("finally.return 后的代码不执行")
}

console.log(fun())
// 报错信息
// finally.return 相当于上一级的 return

A complete error prompt has at least three steps

• Error: Create an error object
• throw: throw (trigger) an error
• try...catch: catch (handle) errors

General usage demonstration

function fun() {
    
    
	// new Error() 创建一个错误对象
	// 用 throw 抛出一个错误
	throw new ReferenceError("这是一个报错信息")
}

try {
    
    
	// 在 try 中执行一个可以报错的函数
	fun()
} catch(error) {
    
    
	// 函数如期抛出错误, 并被 catch 捕获

	// 打印捕获的报错信息
	console.log(error)
}

Error prompt three consecutive

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