this is code of the book(DOM Scripting Web Design with JavaScript and the Doucment Object Model), the way to make the method of getElementByClassName to be true;

getElementByClassName.js

function getElementByClassName (node,classname) {
  if (node.getElementByClassName) {
    return node.getElementByClassName(classname);
  } else {
    var elems = getElementByTagName("*");
    var results = []; 
    for (var i = 0; i < elems.length; i++) {
      if (elems[i].className.indexOf(classname) != -1) {
        results.push(elems[i]);
      }
    }
    return results;
  }
}

即使是这样一段简单的代码,我也错了三个地方;
妈的,智障.