Trying to capitalize the first character in array of strings, why this is not working?

You have to actually re-assign the array element:

    for(var i = 1 ; i < newArr.length ; i++){
        newArr[i] = newArr[i].charAt(0).toUpperCase();
    }       

The "toUpperCase()" function returns the new string but does not modify the original.

You might want to check to make sure that newArr[i] is the empty string first, in case you get an input string with two consecutive dashes.

edit — noted SO contributor @lonesomeday correctly points out that you also need to glue the rest of each string back on:

         newArr[i] = newArr[i].charAt(0).toUpperCase() + newArr[i].substr(1);

Here is my solution with ES6. This is an example where I store the days of the week in my array and I uppercase them with for... of loop.

const days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];

for (let day of days) {
    day = day.charAt(0).toUpperCase() + day.substr(1);
    console.log(day);
}

Here is a link to the documentation: for... of loop documentation

In your for loop, you need to replace the value of newArr[i] instead of simply evaluating it:

for(var i = 1 ; i < newArr.length ; i++){
    newArr[i] = newArr[i].charAt(0).toUpperCase() + newArr[i].substr(1);
}