[原]创建三个输入文本框，当光标离开文本框的时候如果文本框为空，则将文本框背景色设置为红色，如果不为空则为白色。提示：焦点进入控件的事件是onfocus，焦点离开控件的事件是onblur

window.onload = function () {
            var txts = document.getElementsByTagName('input');
            for (var i = 0; i < txts.length; i++) {
                txts[i].onblur = function () {
                    if (this.value.length == 0) {
                        this.style.backgroundColor = 'red';
                    }
                    else {
                        this.style.backgroundColor = '';
                    }
                }
            }
        }
<input type="text" name="name" value="" />
    <input type="text" name="name" value="" />
<input type="text" name="name" value="" />