js把正在点击的输入栏变换背景颜色搜索

<script>
window.onload = function(){
listenInputFocus();
listenTextareaFocus();
}
//点击input后改变背景颜色
listenInputFocus = function(){
var inputs = document.getElementsByTagName("input");
for (var i = 0; i < inputs.length; i++) {
inputs[i].onfocus = function(){
this.style.backgroundColor = '#fff';
}
}
}
//点击textarea后改变背景颜色
listenTextareaFocus = function(){
var textareas = document.getElementsByTagName("textarea");
for (var tex = 0; tex < textareas.length; tex++) {
textareas[tex].onfocus = function(){
this.style.backgroundColor = '#fff';
}
}
}
</script>