年份格式需要在javascript中输入4位.subscript [英] Year format requires to enter 4 digits .subscript in javascript

问题描述

大家好



我有一个即将开展的项目。



我有一个验证程序要写，初学者的水平。



我编写了大部分代码，但是如果用户以2位数形式输入年份，我需要将其转换为4位数字表格。



然后我需要声明一个新变量并使用'.subscript'从国家识别号码中提取4位数字，这是一个13位数字。



我到目前为止编写了大部分代码（我不会在这里发布所有代码），但代码在达到yearString =时不会执行yearString.substring（2,4）。





基本上我需要声明的yearString变量并且工作4位数，即1987年。



显然它不起作用，因为1987 = [1，9，8，7]是一个4字符串数组， AS 我在索引4处没有字符串。



我希望我已经让自己明白了无知的奥利。我会留下来纠正。



Greets。



我尝试过：

Hi guys

I have an upcoming project.

I have a validation program to write, beginner's level.

I've written the code most part, but in case the user inputs the year in 2 digit form I need to convert it into 4-digit form.

Then I need to declare a new variable and extract using '.subscript' the 4-digits from the National Identification Number which is a 13 digit number.

I've written most of the code so far ( I won't post it all of it here), but the code won't execute when it reaches yearString = yearString.substring(2,4).


Basically I need the yearString variable declared and working for a 4 digit year, i.e. 1987.

Obviously it won't work, as 1987 = ["1", "9", "8", "7"] is a 4 string array, AS I don't have a string at index 4.

I hope I've made myself understood and sorry for the ignorance. I stay to be corrected.

Greets.

What I have tried:

function cnpVal() {
    var cnpString = document.getElementById('lblcnp').value;  //13 digit number
    var dayString = document.getElementById('txtday').value;
    var monthString = document.getElementById('txtmonth').value;
    var yearString = document.getElementById('txtyear').value;

    arrayCnp = cnpString.split('');
    
    
    if (yearString.length != 4) {
        alert("Year format requires you to enter 4 digits");
        return false;
        }
        else {
            yearString = yearString.substring(2,4);
        }

推荐答案

Quote：

显然它不起作用，因为1987 = [1，9，8，7]是一个4字符串数组，但我在索引4处没有字符串。

Obviously it won't work as 1987 = ["1", "9", "8", "7"] is a 4 string array, but I don't have a string at index 4.

显而易见！数组中的第一个元素位于索引0（零）。



JavaScript数组 [ ^ ]

JavaScript String substring（）方法 [ ^ ]

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