javascript - Looping through a checkbox array that has one element - Stack Overflow

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I have a list of dynamically created checkboxes named "tags" which I loop through with javascript to make sure only 1 is checked and to get the value. If for some reason this list of checkboxes only has 1 item, my script won't look at it. When I alert the tag's length I get undefined.

    var total=[];
    for (var i=0; i < document.form1.tags.length; i++){
        if(document.form1.tags[i].checked==true){
            total.push(document.form1.tags[i].value);
        }
    }

    if(total.length==0){
        alert("Please select a product to edit.");
    }else if (total.length>1){
        alert("Please select only one product to edit.");
    }else{
        document.location = "go somewhere";
    }

I have a list of dynamically created checkboxes named "tags" which I loop through with javascript to make sure only 1 is checked and to get the value. If for some reason this list of checkboxes only has 1 item, my script won't look at it. When I alert the tag's length I get undefined.

    var total=[];
    for (var i=0; i < document.form1.tags.length; i++){
        if(document.form1.tags[i].checked==true){
            total.push(document.form1.tags[i].value);
        }
    }

    if(total.length==0){
        alert("Please select a product to edit.");
    }else if (total.length>1){
        alert("Please select only one product to edit.");
    }else{
        document.location = "go somewhere";
    }

• javascript
• forms
• checkbox

Share Improve this question Follow asked Nov 8, 2012 at 22:12 KenroKenro 3311 gold badge11 silver badge33 bronze badges 2

• 2 .tags is not an array when there is only one checkbox, it contains direct reference to the one checkbox. It only bees a nodelist when there are more than one checkboxes with the same name. You should always look at the developer console and you would have seen the error there. – Esailija Commented Nov 8, 2012 at 22:14
• @Esailija Yet another reason to use querySelectorAll or jQuery. – John Dvorak Commented Nov 8, 2012 at 22:16

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4 Answers 4

Sorted by: Reset to default 4

Why do you need Checkboxes? Wouldn't this be a great opportunity to use Radiobuttons?

Two suggestions:

1. use getElementsByName instead to get all the elements so you can iterate them:

2. Use a framework like jquery. Any reason you can't use jquery or another framework? Your life would be so much easier.

var tags = document.getElementsByName('tags');
for(var i = 0; i < tags.length; ++i)
{
    if(tags[i].checked) .....
}

You want radio buttons.

<input type='radio' name='tags' value='[whatever]' />

You won't have to 'check and make sure only one is selected'. And to get the

var tags = document.getElementsByName('tags'),
    value = '', i = 0;

for( ; i < tags.length; i++ )
{
    if( tags[i].checked ) {
        value = tags[i].value;
        break;
    }
}

from the top of my head... if there is only one checkbox selected it might be document.form1.tags is not an array...

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