JS检查当图片不存在时显示默认图片和键盘大小写键状态

当图片不存在时显示默认图片

<script type="text/javascript"> 
        var imgs = document.images; 
        for(var i = 0;i < imgs.length;i++){ 
            imgs[i].onerror = function(){ 
                this.src = "http://images2015.cnblogs.com/blog/66516/201511/66516-20151104233425055-1712623285.png"; 
            } 
        } 
</script>

或者：

<img src="" border="0" onerror="this.src=' http://images2015.cnblogs.com/blog/66516/201511/66516-20151104233425055-1712623285.png'"/>

键盘大小写键状态

<script type="text/javascript">
            function detectCapsLock(event) {
                var e = event || window.event;
                var o = e.target || e.srcElement;
                var oTip = o.nextSibling;
                var keyCode = e.keyCode || e.which; // 按键的keyCode 
                var isShift = e.shiftKey || (keyCode == 16) || false; // shift键是否按住
                if (
                    ((keyCode >= 65 && keyCode <= 90) && !isShift) // Caps Lock 打开，且没有按住shift键 
                    || ((keyCode >= 97 && keyCode <= 122) && isShift)// Caps Lock 打开，且按住shift键
                ) {
                    oTip.style.display = '';
                }
                else {
                    oTip.style.display = 'none';
                }
            }
 
            window.onload = function () {
                document.getElementById('<%= txtUserName.ClientID %>').focus();
                document.getElementById('<%= txtPassword.ClientID %>').onkeypress = detectCapsLock;
            };
</script>