js将字符串中的每一个单词的首字母变为大写其余均为小写

function titleCase(str) {
 var newarr,newarr1=[]; 
 newarr = str . toLowerCase() . split(" ");
 for(var i = 0 ; i < newarr . length ; i++){
 newarr1 . push(newarr[i][0] . toUpperCase()+newarr[i] . substring(1));
 }
 return newarr1.join(' ');
}
titleCase("I'm a little tea pot");

function titleCase(str) {
 var newarr,newarr1; 
 newarr =str.toLowerCase().split(" ");
 for(var i=0;i<newarr.length;i++){
 newarr[i] = newarr[i][0].toUpperCase()+newarr[i].substring(1,newarr[i].length));
 }
 newarr1 = newarr.join(" ");
 return newarr1;
}
titleCase("I'm a little tea pot");