Javascript behaving weirdly

the following function does not work as I thought it should have. For some reason, the loop breaks whenever one the the validate function returns false. Why is that?

Here is my code :

function validateGroup(input) {
    if (!input.value.match(/^[0-9]{0,2}$/)) {
        $(input).addClass("invalidField");
        return false;
    }
    $(input).removeClass("invalidField");
    return true;
}

function validateClass(input) {
    if (!input.value.match(/^[a-zA-Z0-9-]{0,9}$/)) {
        $(input).addClass("invalidField");
        return false;
    }
    $(input).removeClass("invalidField");
    return true;    
}

function validateData() {
    var rows = document.getElementsByTagName("tbody")[0].getElementsByTagName("tr");

    var valid = true;

    for (var i = 0, arrayLength = rows.length; i < arrayLength; ++i) {
        valid = valid && validateClass(rows[i].getElementsByTagName("input")[0]);
        valid = valid && validateGroup(row开发者_开发技巧s[i].getElementsByTagName("input")[1]);
        valid = valid && validateGroup(rows[i].getElementsByTagName("input")[2]);     
    }
    return valid;
}

Thanks a lot!

the statement valid && validateClass(...) will not call the validateClass method if valid is false. I think what you want to do is change the order of those to

valid = validateClass(rows[i].getElementsByTagName("input")[0]) && valid;
valid = validateGroup(rows[i].getElementsByTagName("input")[1]) && valid;
valid = validateGroup(rows[i].getElementsByTagName("input")[2]) && valid;

Javascript doesn't bother evaluating the rest of an && expression if it already knows that the result is false.

It looks like you want to run the validate functions on each iteration even if ‘valid’ was already set to false. However the && operation you are using will short-circuit, so although the loop will continue the validate functions will not be called on subsequent iterations.

A really simple alternative which would work the way you want would be:

for (var i = 0, arrayLength = rows.length; i < arrayLength; ++i) {
   if(!validateClass(rows[i].getElementsByTagName("input")[0]))  valid = false;
   if(!validateGroup(rows[i].getElementsByTagName("input")[1]))  valid = false;
   if(!vvalidateGroup(rows[i].getElementsByTagName("input")[2])) valid = false;
}

It sounds like that is the intent of the function. The three lines of

valid = valid && validate...

mean that if any of the validate functions ever hits false valid will remain false for the rest of the loop.

I think it's because of the lazy evaluation scheme Javascript uses with &&. Try a single & instead.

Short-circuit evaluation: Support in common programming languages

It's called short-circuiting. Quick fix: replace each line with

valid = validateClass(rows[i].getElementsByTagName("input")[0]) && valid;