CODEWITHSUNDEEP
jquery
alias51
alias51

Reputation: 8608

Basic var syntax: Variable already defined?

I have the following code, which tests if an element is present in the browser viewport:

(function ($) {
$.fn.visible = function (partial, hidden, direction) {

    var $t = $(this).eq(0),
        t = $t.get(0),
        $w = $(window),
        viewTop = $w.scrollTop(),
        viewBottom = viewTop + $w.height(),
        viewLeft = $w.scrollLeft(),
        viewRight = viewLeft + $w.width(),
        _top = $t.offset().top,
        _bottom = _top + $t.height(),
        _left = $t.offset().left,
        _right = _left + $t.width(),
        compareTop = partial === true ? _bottom : _top,
        compareBottom = partial === true ? _top : _bottom,
        compareLeft = partial === true ? _right : _left,
        compareRight = partial === true ? _left : _right,
        clientSize = hidden === true ? t.offsetWidth * t.offsetHeight : true,
        direction = (direction) ? direction : 'both';

    if (direction === 'both') return !!clientSize && ((compareBottom <= viewBottom) && (compareTop >= viewTop)) && ((compareRight <= viewRight) && (compareLeft >= viewLeft));
    else if (direction === 'vertical') return !!clientSize && ((compareBottom <= viewBottom) && (compareTop >= viewTop));
    else if (direction === 'horizontal') return !!clientSize && ((compareRight <= viewRight) && (compareLeft >= viewLeft));
};

})(jQuery);

However, when I run this through JS lint, I get an error stating that direction is already defined. Where is my syntax wrong?

(The script still works)

Upvotes: 1

Views: 114

Answers (2)

Chris
Chris

Reputation: 7855

Its because direction is already a paremeter to your function. And then in the var statement youre declaring it again. try:

[...]
clientSize = hidden === true ? t.offsetWidth * t.offsetHeight : true;
direction = (direction) ? direction : 'both';
[...]

for example. (Changed the , to a ;) that will make the direction line a new assertion statement itsself without a var keyword.

b.t.w.

statements like your assertion to direction can be shortened like this:

direction = direction || 'both';

this will result in 'both' beeing assigned to direction if direction is undefined or any other falsy value.

Upvotes: 1

Felix Kling
Felix Kling

Reputation: 816462

direction is the parameter name and you are defining it inside the function with var direction.

If you change the comma of the previous line to a semicolon, i.e. make direction = ... not part of the var statement, you'll be fine.

Upvotes: 4

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