轻单JK快捷键

shortcut.js

(function(){
    var style = document.createElement('style');
    style.innerHTML = '.container ol.items li .title[shortcut] { border-color:#66afe9;box-shadow:inset 0 1px 1px rgba(0,0,0,.075),0 0 8px rgba(102,175,233,.6); }';
    document.head.appendChild(style);
    var length = document.querySelector('ol.items').children.length;
    var index = 0;

    var inc = function(){
        return index >= length ? index = length : index++; 
    }

    var dec = function(){
        return index <= 0 ? index = 0 : index--; 
    }

    var mark = function(bool){
        document.querySelector('ol.items li:nth-child('+(index)+') .title')[(bool?'set':'remove')+'Attribute']('shortcut','');
    };

    var nav = function(direction){
        (index>0 && index<=length) && mark(false);
        direction=='next'?inc():dec();
        if(index !== 0){
            mark(true);
            scroll();
        }else{
            scroll(1);
        }
    };

    var scroll = function(top){
        var top = top || document.querySelector('ol.items li:nth-child('+index+') .title').getBoundingClientRect().top - document.body.getBoundingClientRect().top - document.querySelector('#sectionHeader').getBoundingClientRect().height - 15;
        window.scrollTo(0,top);
    };

    var onKeydown = function(ev){
        switch(ev.keyCode){
            case 74: // j
                nav('next');
                break;
            case 75: // k
                nav('prev');
                break;
            default:
                break;
        }
    }

    document.addEventListener('keydown',onKeydown,false);
})();