Question

So I have an if statement, and I want it so that if the condition is true, an error is thrown. It’s a form for users to remove items from an array called myArr, and if that item does not exist in myArr I want it to throw an error.

$('#remove_user').submit(function(){
    id = $('#user_num').val();
    diffVal = $.grep(myArr, function(value, i){
        return value != id;
    });
    if (diffVal.length == myArr.length) {
        //I want the error here to say "Does not exist."
    } else {
        myArr = diffVal
    };
    $('#user_list').html('');
    for (var i=0; i < myArr.length; i += 1) {
        $('#user_list').append('<li>' +myArr[i]+ '</li>');
    };
    return false;
});

Answer 1

You can use

throw "Item does not exist!"

But I’ve found that it’s better to throw an Error object, like so:

throw new Error("Item does not exist!");

If you throw an Error you get marginally better tracibility. Error handling in JavaScript is sadly still abysmal.