web前端校招笔试题集锦

写一个求和的函数sum，达到下面的效果

// Should equal 15
sum(1, 2, 3, 4, 5);
// Should equal 0
sum(5, null, -5);
// Should equal 10
sum(‘1.0‘, false, 1, true, 1, ‘A‘, 1, ‘B‘, 1, ‘C‘, 1, ‘D‘, 1,
  ‘E‘, 1, ‘F‘, 1, ‘G‘, 1);
// Should equal 0.3, not 0.30000000000000004
sum(0.1, 0.2);

function sum() {
    var nResult = 0;
    for (var i = 0, l = arguments.length; i < l; i++) {
        nResult += window.parseFloat(arguments[i]) || 0;
    }
    return nResult.toFixed(3) * 1000 / 1000;
}

请写一个表格以及对应的CSS，使表格奇数行为白色背景，偶数行为灰色背景，鼠标移上去时为黄色背景。

<table class="table">
  <tr><td>第一行</td></tr>
  <tr><td>第二行</td></tr>
  <tr><td>第三行</td></tr>
  <tr><td>第四行</td></tr>
</table>

<style>
  .table tr:nth-child(2n-1){
      background-color:white;
  }
  .table tr:nth-child(2n){
      background-color:grey;
  }
  .table tr:hover{
      background-color:yellow;
  }
</style>

写一个traverse函数，输出所有页面宽度和高度大于50像素的节点。

function traverse(oNode) {
    var aResult = [];
    oNode = oNode || document.body;
    if (oNode.style) {
        var nWidth = window.parseInt(oNode.style.width, 10) || 0;
        var nHeight = window.parseInt(oNode.style.height, 10) || 0;
        if (nWidth > 50 && nHeight > 50) {
            aResult.push(oNode);
        }
    }
    var aChildNodes = oNode.childNodes;
    if (aChildNodes.length > 0) {
        for (var i = 0, l = aChildNodes.length; i < l; i++) {
            var oTmp = aChildNodes[i];
            aResult = aResult.concat(traverse(oTmp));
        }
    }
    return aResult;
}