CODEWITHSUNDEEP
javascriptarrays
dottedquad
dottedquad

Reputation: 1391

Javascript: How do I splice a value from an array with an index of 0?


I am attempting to remove a value from an array using splice. starting at 0 and ending at 0 splice, but it is not removing the value at index 0. I added a function getItemRow to check the species index which returns 0. I dumped the values of the array into an alert and it still outputs species which should of been deleted. invalidElement.splice(indexValue, indexValue); works as expected for indexes that are NOT 0. Why is this happening and how do I delete the value that has 0 index?

javascript code: 

var invalidElement = new Array("species", "alias", "gender", "breeding", "birth_date");

//This function will be removed once fixed!!
function getItemRow()
{
    var myPosition=-1
    for (i=0;i<invalidElement.length;i++)
    {
        if(invalidElement[i]=="species") {
            myPosition = i;
            break;
        }
    }
    alert(myPosition)
}

function validateElement(formId, element, selector, errorContainer)
{
    getItemRow()//for testing purposes
    //var indexValue = $.inArray(element, invalidElement);
    var indexValue = invalidElement.indexOf(element);

    alert(element);
    $.ajax({
        type: 'POST',
        cache: false,
        url: "validate_livestock/validate_form/field/" + element,
        data: element+"="+$(selector).val(),
        context: document.body,
        dataType: 'html',
        success: function(data){
            if (data == "false")
            {
                $(errorContainer).removeClass('element_valid').addClass('element_error');
                invalidElement = element;
                alert(invalidElement.join('\n'))//for testing purposes
                //alert(indexValue);
            }
            else
            {
                $(errorContainer).removeClass('element_error').addClass('element_valid');
                invalidElement.splice(indexValue, indexValue);
                alert(invalidElement.length);//for testing purposes
                alert(invalidElement.join('\n'))//for testing purposes
            }
        }
    });
}

$("#species").change(function(){
    validateElement('#add_livestock', 'species', '#species', '.species_error_1')
});

Upvotes: 13

Views: 43123

Answers (4)

STW
STW

Reputation: 46366

Splice can work in two modes; to remove or insert items.

When removing items you'll specify two parameters: splice(index, length) where index is the starting index, and length is a positive number of elements to remove (fyi: passing a "0", as in your example, does nothing--it's saying "remove zero items starting at index"). In your case you'll want:

invalidElement.splice(indexValue, 1); // Remove 1 element starting at indexValue

When inserting items you'll specify (at least) three parameters: splice(index, length, newElement, *additionalNewElements*). In this overload you normally pass 0 as a 2nd parameter, meaning to insert the new elements between existing elements.

 var invalidElements = ["Invalid2", "Invalid3"];
 invalidElements = invalidElements.splice(0, 0, "Invalid1");

Upvotes: 14

David Tang
David Tang

Reputation: 93674

There's also a convenience function for removing the first element in an array:

array.shift();

See: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/shift.

Upvotes: 11

typo.pl
typo.pl

Reputation: 8942

Mozilla Dev Center - Array.splice states that the second parameter is 'howMany' elements to remove.

I'm not sure how your code worked when it passed in the indexValue as the number of elements to remove, unless you were removing from the end of the array.

Upvotes: 0

alex
alex

Reputation: 490263

I think you want splice(0, 1).

The second argument is how many you want removed...

An integer indicating the number of old array elements to remove. If howMany is 0, no elements are removed.

Source.

Upvotes: 16

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