代码改变世界

js数据强转

2020-03-31 22:06  默默不语  阅读(217)  评论(0)    收藏  举报 
<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title></title>
        <script type="text/javascript">
            /* 强转 */
            /* 1.其他类型转为Number类型 */
            var s1 = "10";
            var s2 = "abc";
            var b1 = false;
            var o1 = Object(10);
            var o2 = new Array();
            o2[0]=1;
            o2[1]=2;
            var o3 = null;
            document.write("String转number，可转："+Number(s1)+"<br>");//10
            document.write("String转number，不可转："+Number(s2)+"<br>");//Nan
            document.write("boolean转number，可转："+Number(b1)+"<br>");//0
            document.write("Object转number=："+Number(o2)+"<br>");//若o2中只有o2[0]，则为1，若还有o2[1]，则为NaN
            document.write("null转number："+Number(o3)+"<br>");//0
            /* 能转就转，不能转就为NaN， */
            /* 2.其他类型转为boolean类型 */
            var nb = 10;
            var sb = "abc";
            var ob = new Object(1);
            var unb;
            //2.1Number转Boolean
            document.write("Number转Boolean："+Boolean(nb)+"<br>");//非零转成true，0转成false
            //2.2String转Boolean
            document.write("String转Boolean："+Boolean(sb)+"<br>");//非空转成true，空转成false
            //2.3Object转Boolean
            document.write("Object转Boolean："+Boolean(ob)+"<br>");//非null转成true，null转成false
            //2.4声明未赋值(undefined)转Boolean
            document.write("声明未赋值(undefined)转Boolean："+Boolean(unb)+"<br>");//false

        </script>
    </head>
    <body>
    </body>
</html>

 

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title></title>
        <script type="text/javascript">
            /* 3.boolean转String */
            var b = true;
            document.write("Boolean转String："+typeof(b.toString())+"<br>");//String
            /* 4.String转Number */
            var s = "10";
            document.write("String转Number："+typeof(parseInt(s) )+"<br>");//number
        </script>
    </head>
    <body>
    </body>
</html>