将字符串的首字母变为大写

 var string="bai-jia-xiu"
        console.log("bai-jia-xiu")
        var str=string.split('-')
        var arr=[]
        for(var i=0;i<str.length;i++){
            toCase(str[i])
        }
        function toCase(a){
            var s1 = a.substring(0, 1);
            var s2 = a.substring(1,a.length)
            var s3 = s1.toUpperCase();
            var s4 = s3.concat(s2)
            arr.push(s4)
        }
        var finshedStr=arr.map((item)=>item).join('')
        console.log(finshedStr)