javascript三元运算符，以增加或减少值

Question

The only difference in the following code are the - and + symbols used to increase or subtract the value.

if( that.hasClass('prev') ){
    $('.elem').scrollLeft( $('.elem').scrollLeft()-(0.1*factor) );
}
else if( that.hasClass('next') ){
    $('.elem').scrollLeft( $('.elem').scrollLeft()+(0.1*factor) );
}

I would like to know how to convert the code in a small ternary statement, is it possible?

Answer 1

If you really need to test both classes ("next" and "prev"), you can factor out the logic:

var mul = that.hasClass("prev") ? -1 :
          that.hasClass("next") ? 1 :
          0;

$(".elem").scrollLeft($(".elem").scrollLeft() + mul * 0.1 * factor);

You could turn that into a jQuery function if you felt particularly energetic:

$.fn.scrollDir = function() {
  return  that.hasClass("prev") ? -1 :
          that.hasClass("next") ? 1 :
          0;
};

$(".elem").scrollLeft($(".elem").scrollLeft() + that.scrollDir() * 0.1 * factor);

Answer 2

If you really want to do this the following should work:

$('.elem').scrollLeft($('.elem').scrollLeft()+(0.1*factor*(that.hasClass('prev') ? -1 : that.hasClass('next') ? 1 : 0)))

But for clarity, I'd probably leave it as you have written.

Answer 3

我会这样做

(that.hasClass('prev')) ? $('.elem').scrollLeft( $('.elem').scrollLeft()-(0.1*factor) ) : $('.elem').scrollLeft( $('.elem').scrollLeft()+(0.1*factor) );