javascript - 创建一个类的实例时，如何找出传递的参数数量？ [重复](How to find out the number of arguments passed when creating an instance of a class? [duplicate])

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(This question already has answers here) : ((这个问题已经在这里有了答案) ：)

How best to determine if an argument is not sent to the JavaScript function (12 answers) (如何最好地确定参数是否未发送到JavaScript函数 （12个答案）)

Closed 5 hours ago . (5小时前关闭。)

I need to make my custom error.(我需要进行自定义错误。)

If the arguments are not numbers and if the arguments alength are more or less than two, then an error occurs.(如果参数不是数字，并且参数alength大于或小于2，则会发生错误。) class Point { constructor(x, y) { this.x = x; this.y = y; this.isNum(); } isNum() { if(typeof this.x !== 'number' || typeof this.y !== 'number' ) { throw new Error('point is not a number ') } console.log(arguments.length) } } try{ let example = new Point(1,2) } catch(e){ console.error(e) } console.log(example.arguments.length) How do I know the length of the arguments?(我怎么知道参数的长度？) Is this spelling wrong?(这是拼写错误吗？) If you can show how to solve correctly?(如果可以显示如何正确解决？) I apologize if I crookedly wrote a question.(如果我歪曲了一个问题，我深表歉意。)   ask by incognita translate from so

Answer 1

Using arguments object(使用arguments对象)

Note: example is defined inside try with let which cant be accessed from outside of scope(注意： example是在try中定义的，其中let不能从范围外部访问) class Point { constructor(x, y) { this.x = x; this.y = y; this.arguments = arguments; this.isNum(); } isNum() { if (this.arguments.length != 2) { throw new Error('you send more arguments') } if (typeof this.x !== 'number' || typeof this.y !== 'number') { throw new Error('point is not a number ') } } } try { let example = new Point(1, 2) console.log(example.arguments.length) } catch (e) { console.error(e) }