공통 원생 js 함수

1. 뷰포트 너비 가져오기

    getViewportWidth: function(){
        var pageWidth = window.innerWidth;
        if (typeof pageWidth != "number"){
            if (document.compatMode == "CSS1Compat"){
                pageWidth = document.documentElement.clientWidth;
            } else {
                pageWidth = document.body.clientWidth;
            }
        }
        return pageWidth;
    }

2.브라우저 간 이벤트 처리

    EventUtil: {
        addHandler: function(element,type,handler){
            if(element.addEventListener){
                element.addEventListener(type,handler,false);
            }else if(element.attachEvent){
                element.attachEvent('on'+type, handler);
            }else{
                element["on"+type] = handler;
            }
        },
        removeHandler: function(element,type,handler){
            if(element.removeEventListener){
                element.removeEventListener(type,handler,false);
            }else if(element.detachEvent){
                element.detachEvent('on'+type, handler);
            }else{
                element["on"+type] = null;
            }
        },
        getEvent: function(event){
            return event? event:window.event;
        },
        getTarget: function(event){
            return event.target || event.srcElement;
        },
        preventDefault: function(event){
            if(event.preventDefault){
                event.preventDefault();
            }else{
                event.returnValue = false;
            }
        },
        stopPropagation: function(event){
            if(event.stopPropagation){
                event.stopPropagation();
            }else{
                event.cancelBubble = true;
            }
        },
    }

3. 브라우저에서 요소 거리 페이지의 맨 왼쪽과 맨 위 거리 얻기

function getElementLeft(element){
    var actualLeft = element.offsetLeft;
    var current = element.offsetParent;
    while(current!==null){
        actualLeft += current.offsetLeft;
        current = current.offsetParent;
    }
    return actualLeft;
}

function getElementTop(element){
    var actualTop = element.offsetTop;
    var current = element.offsetParent;
    while(current!==null){
        actualTop += current.offsetTop;
        current = current.offsetParent;
    }
    return actualLeft;
}

4. 브라우저 간 getBoundingClientRect 함수

// ，ie8 （2，2）
function getBoundingClientRect(element){
    var scrollTop = document.documentElement.scrollTop;
    var scrollLeft = document.documentElement.scrollLeft;

    if(element.getBoundingClientRect){
        if(typeof arguments.callee.offset != 'number'){
            var scrollTop = document.documentElement.scrollTop;
            var temp = document.createElement('div');
            temp.style.cssText = "position:absolute; left:0; right:0;";
            document.body.appendChid(temp);
            arguments.callee.offset = -temp.getBoundingClientRect().top
                                    -scrollTop;
            document.body.removeChild(temp);
            temp = null;
        }
        var rect = element.getBoundingClientRect();
        var offset = arguments.callee.offset;
        return {
            left: rect.left + offset,
            top: rect.top + offset,
            right: rect.right + offset,
            bottom: rect.bottom + offset,
        }
    }else{
        var actualLeft = getElementLeft(element);
        var actualTop = getElementTop(element);
        return {
            left: actualLeft - scrollLeft,
            top: actualTop - scrollTop,
            right: actualLeft + element.offsetWidth -scrollLeft;
            bottom: actualTop + element.offsetHeight - scrollTop;
        }
    }
}

5. 요소가 뷰포트 범위 내에 있는지 확인

const inViewport = (el) => {
  const rect = el.getBoundingClientRect()

  return rect.top > 0
    && rect.bottom < window.innerHeight
    && rect.left > 0
    && rect.right < window.innerWidth
}