html 树形怎么实现 键盘上下左右 切换 用JS 实现

Question

Answer 1

 window.onload = function() {
    var oBox = document.getElementById("box");
    var bLeft = bTop = bRight = bBottom = bCtrlKey = false;
    setInterval(function() {
        if (bLeft) {
            oBox.style.left = oBox.offsetLeft - 10 + "px"
        } else if (bRight) {
            oBox.style.left = oBox.offsetLeft + 10 + "px"
        }
        if (bTop) {
            oBox.style.top = oBox.offsetTop - 10 + "px"
        } else if (bBottom) {
            oBox.style.top = oBox.offsetTop + 10 + "px"
        }
        limit();
    },
    30);
    document.onkeydown = function(event) {
        var event = event || window.event;
        bCtrlKey = event.ctrlKey;
        switch (event.keyCode) {
        case 37:
            bLeft = true;
            break;
        case 38:
            if (bCtrlKey) {
                var oldWidth = oBox.offsetWidth;
                var oldHeight = oBox.offsetHeight;
                oBox.style.width = oBox.offsetWidth * 1.5 + "px";
                oBox.style.height = oBox.offsetHeight * 1.5 + "px";
                oBox.style.left = oBox.offsetLeft - (oBox.offsetWidth - oldWidth) / 2 + "px";
                oBox.style.top = oBox.offsetTop - (oBox.offsetHeight - oldHeight) / 2 + "px";
                break;
            }
            bTop = true;
            break;
        case 39:
            bRight = true;
            break;
        case 40:
            if (bCtrlKey) {
                var oldWidth = oBox.offsetWidth;
                var oldHeight = oBox.offsetHeight;
                oBox.style.width = oBox.offsetWidth * 0.75 + "px";
                oBox.style.height = oBox.offsetHeight * 0.75 + "px";
                oBox.style.left = oBox.offsetLeft - (oBox.offsetWidth - oldWidth) / 2 + "px";
                oBox.style.top = oBox.offsetTop - (oBox.offsetHeight - oldHeight) / 2 + "px";
                break;
            }
            bBottom = true;
            break;
        case 49:
            bCtrlKey && (oBox.style.background = "green");
            break;
        case 50:
            bCtrlKey && (oBox.style.background = "yellow");
            break;
        case 51:
            bCtrlKey && (oBox.style.background = "blue");
            break;
        }
        return false
    };
    document.onkeyup = function(event) {
        switch ((event || window.event).keyCode) {
        case 37:
            bLeft = false;
            break;
        case 38:
            bTop = false;
            break;
        case 39:
            bRight = false;
            break;
        case 40:
            bBottom = false;
            break;
        }
    };
    function limit() {
        var doc = [document.documentElement.clientWidth, document.documentElement.clientHeight] oBox.offsetLeft <= 0 && (oBox.style.left = 0);
        oBox.offsetTop <= 0 && (oBox.style.top = 0);
        doc[0] - oBox.offsetLeft - oBox.offsetWidth <= 0 && (oBox.style.left = doc[0] - oBox.offsetWidth + "px");
        doc[1] - oBox.offsetTop - oBox.offsetHeight <= 0 && (oBox.style.top = doc[1] - oBox.offsetHeight + "px")
    }
};