Javascript檢查是否設置了陣列

Question

我有一個表單驗證腳本，用於驗證是否至少選中了1個複選框。

<form name="samples" onsubmit="return validateForm();" action="process.php" method="post"> 
    <input type="checkbox" name="products[]" value="product-a"> 
    <input type="checkbox" name="products[]" value="product-b"> 
    <input type="checkbox" name="products[]" value="product-c"> 
</form> 

<script> 
function validateForm() { 
    var counter = document.forms["samples"]["products"].value; 
    if (x == null || x == "") { 
     alert("Please select at least one product"); 
     return false; 
    } 
} 
</script> 

上面的代碼似乎不起作用。

我在做什麼錯？

Answer 1

<script type = "text/javascript"> 
function validateForm() { 
var flag = false; 
var products = document.samples["products[]"]; 
for (var i = 0; i<products.length; i++) { 
    if(products[i].checked){ 
     flag = true; 
    } 
} 
if (flag != true) { 
    alert("Please select at least one product"); 
    return false; 
} 
return true; 
} 
</script> 

Answer 2

你有名字products沒有輸入元素，你做有名字products[]

arrayOfProductInputs = document.forms["samples"]["products[]"]; 
// ^^^ loop through those 

元素總數：

function validateCheckboxes() { 
    var arrayOfProductInputs = document.forms["samples"]["products[]"]; 
    var productsChecked = 0; 
    arrayOfProductInputs.forEach(function(itm){ 
     if(itm.checked) productsChecked++; 
    }); 

    if(productsChecked <= 0) { 
     alert("Please select at least one product"); 
     return false; 
    } 
    return true; 
}