SOURCE

function countNumber(stringtoCount){
var num=0;
for(var i=0;i<stringtoCount.length;i++){
var char=stringtoCount.charAt(i);
//isNaN()对空格字符会转化为0，需要加个判断charAt(1)不能为
if(char!=""&!isNaN(char)){
num++;
}
}
return num;
}
document. write("5S3F6CE79SL里面有" +countNumber("5S3F6CE79SL") + "个数字");