在JS中驗證日期？

Question

試圖做這個日期驗證，這是我想出的代碼。它似乎沒有工作。任何幫助，將不勝感激。

function isValidDate(dateStr) { 
    // Checks for the following valid date formats: 
    // MM/DD/YY MM/DD/YYYY MM-DD-YY MM-DD-YYYY 

    var dateStr = document.getElementById("dob").value; 

    var datePat = /^(\d{1,2})(\/|-)(\d{1,2})\2(\d{2}|\d{4})$/; 

    var matchArray = dateStr.match(datePat); 

    if (matchArray == null){ 
     errMsg = errMsg + "Date is not in a valid format."; 
     result = false; 
    } 

    var month = matchArray[1]; 

    var day = matchArray[3]; 

    var year = matchArray[4]; 

    if (month < 1 || month > 12){ 
     errMsg = errMsg + "Month must be between 1 and 12."; 
     result = false; 
    } 

    if (day < 1 || day > 31){ 
     errMsg = errMsg + "Day must be between 1 and 31."; 
     result = false; 
    } 

    if ((month==4 || month==6 || month==9 || month==11) && day==31){ 
     errMsg = errMsg + "Month "+month+" doesn't have 31 days!"; 
     result = false; 
    } 

    if (month == 2){ // check for leap year 

     var isleap = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)); 

     if (day>29 || (day==29 && !isleap)){ 
     errMsg = errMsg + "February " + year + " doesn't have " + day + " days!"; 
     result = false; 
     } 
    } 

    return result;  // date is valid 
} 

Answer 1

爲什麼要補充datestr作爲參數，當你通過

var dateStr = document.getElementById("dob").value; 

訪問它，其次我把一些控制檯，並嘗試運行該功能，並找出你正在月份日期和日期月。只要把console.log並檢查它。其餘的你需要在使用它之前聲明變量，沒有任何變量被初始化，它會這樣做，所有的都可以正常工作。這裏是代碼

<script type="text/javascript"> 
function isValidDate(dateStr) { 
// Checks for the following valid date formats: 
// MM/DD/YY MM/DD/YYYY MM-DD-YY MM-DD-YYYY 

var datePat = /^(\d{1,2})(\/|-)(\d{1,2})\2(\d{2}|\d{4})$/; 

var matchArray = dateStr.match(datePat); 

var errMsg; 

var result = true; 

if (matchArray == null){ 
    errMsg = errMsg + "Date is not in a valid format."; 
    result = false; 
} 

var day= matchArray[1]; 

var month= matchArray[3]; 

var year = matchArray[4]; 


if (month < 1 || month > 12){ 
    errMsg = errMsg + "Month must be between 1 and 12."; 
    result = false; 
} 

if (day < 1 || day > 31){ 
    errMsg = errMsg + "Day must be between 1 and 31."; 
    result = false; 
} 

if ((month==4 || month==6 || month==9 || month==11) && day==31){ 
    errMsg = errMsg + "Month "+month+" doesn't have 31 days!"; 
    result = false; 
} 

if (month == 2){ // check for leap year 

    var isleap = (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)); 

    if (day>29 || (day==29 && !isleap)){ 
    errMsg = errMsg + "February " + year + " doesn't have " + day + " days!"; 
    result = false; 
    } 
} 

console.log(result);  // date is valid 
} 
</script> 

Answer 2

第一個錯誤：在你的函數的頂部不重新定義dateStr如果你在把它當作一個參數 - 否則不把它作爲一個參數。

第二個和第三個錯誤：在函數的開始初始化errMsg = '';和result = true;。

function isValidDate(dateStr) { 
    // Checks for the following valid date formats: 
    // MM/DD/YY MM/DD/YYYY MM-DD-YY MM-DD-YYYY 

// var dateStr = document.getElementById("dob").value; 
    var errMsg = ''; 
    var result = true; 

或：

function isValidDate() { 
    // Checks for the following valid date formats: 
    // MM/DD/YY MM/DD/YYYY MM-DD-YY MM-DD-YYYY 

    var dateStr = document.getElementById("dob").value; 
    var errMsg = ''; 
    var result = true;