Javascript函数没有从输入框获取值并循环遍历数组

Question

im trying to gather an amount from a input box and then tick a certain amount of boxes which is an array.

this is what i got so far and it doesnt work :S

function checkAmount(ting)  {  
var boxes = document.getElementsByTagName("input");  
for (var i = 0; i < ting.value; i++)   {  
    if (boxes[i].name == "vote[]")   {  
        boxes[i].checked = true;  
    }  
}  
}

And im calling it with this:

uncheckAll(); 
checkAmount(document.getElementsByName(\'ammount\'));

Answer 1

getElementsByName returns an array and your function is expecting a single element, you need to access the first element like this:

checkAmount(document.getElementsByName(\'ammount\')[0]); 

Change the ting.value to boxes.length in the for loop:

function checkAmount(ting)  {  
var boxes = document.getElementsByTagName("input");  
for (var i = 0; i < boxes.length; i++)   {  
        boxes[i].checked = (boxes[i].name == "vote[]") ;  
  }  
}

Answer 2

Try using

checked=checked

instead of

checked=true

Answer 3

Try this:

boxes.item(i).checked = checked

sorry not sure how to insert javascript into the post

Answer 4

are you posting your real code? If so, you realize that you are spelling 'amount' wrong in your function call?

From your statement "gather an amount from an input box" I think you expect ting to be a number entered into a text box and so you are calling a function that expects a number with a value that should resolve to an array of form element objects?

var m = document.getElementsByName("amount");

m will be an array!

in other words, it might work better if you made sure you were passing a number when you call checkAmount:

checkAmount(documents.forms[0].amount.value)

or:

checkAmount(documents.getElementsByName("amount")[0].value)

It would help a lot if you post the actual HTML and actual javascript code.

Answer 5

There are several problems with the code you posted, as indicated by the previous answers and replies. Try something like this:

function checkAmount(ting)  {  
    var boxes = document.getElementsByTagName("input");  
    for (var i = 0; i < ting.value && i < boxes.length; i++)   {  
        if (boxes[i].name == "vote[]")   {  
            boxes[i].checked = true;  
        }  
    }  
}

Called like this:

uncheckAll(); 
checkAmount(document.getElementsByName(\'ammount\')[0]);

Now you are safe from array out of bounds errors no matter the value typed in the input field and the call to checkAmount should work.