文本框(input)获取焦点(onfocus)时样式改变的示例代码

 function focusInput(focusClass, normalClass) {
           var elements = document.getElementsByTagName("input");
              for (var i=0; i < elements.length; i++) {
                 if (elements[i].type != "button" && elements[i].type != "submit" && elements[i].type != "reset") {
                 //if(elements[i].type=="text"){
                   elements[i].onfocus = function() { this.className = focusClass; };
                   elements[i].onblur = function() { this.className = normalClass||''; };
                }
             }
        }

        window.onload = function() {
            focusInput('focusInput', 'normalInput');
        }

<style type="text/css">
.normalInput { border:1px solid #ccc; }
.focusInput {    border:1px solid #FFD42C; }
</style>