<script>
    var i="123abc";
    i=parseInt(i);//字符串转整形
    alert(i+","+typeof(i));//输出：123，number
    i="12.3abc";
    i=parseFloat(i);//字符串转浮点型
    alert(i+","+typeof(i));//输出：12.3，number(可见不管是int还是float都是number类型)
    i="a123abc";
    i=parseInt(i);//字符串转整形
    alert(i+","+typeof(i));//输出：NaN，number （由于转换失败，所以提示“不是一个数字，Not a Number”）
    var num=document.getElementById("num").value;
    function showMsg(num)
    {
        for(var i=0;i<num;i++)
        {
            document.write("你好，JavaScript！<br/>");
        }
    }
</script>

javascript闭包入门示例
1.functionsay667(){varnum=666;varsayAlert=function(){alert(num);}num++;returnsayAlert;}varsayAlert=say667();sayAlert();2.functionsetUpSomeGlobals(){varnum=666;gAlertNumber=function(){alert(num);}gIncr

js图片预加载示例
js图片预加载简单示例functionloadImage(url,callback){if(url!='null'){varimg=newImage();img.src=url;if(img.complete){callback(img);}else{img.onload=function(){img.onload=null;callback(img);}}}}

js实现checkbox全选和反选示例
复选框全选示例inputtype="checkbox"name="selectall"value=ononclick="selectAll()"functionselectAll(form){varobj=document.getElementsByName('selectall');varcks=document.getElementsByTagName("input