Javascript sort function. Sort by First then by Second

You could chain the sort order with logical OR.

objects.sort(function (a, b) {
    return a.strength - b.strength || a.name.localeCompare(b.name);
});

This little function is often handy when sorting by multiple keys:

cmp = function(a, b) {
    if (a > b) return +1;
    if (a < b) return -1;
    return 0;
}

or, more concisely,

cmp = (a, b) => (a > b) - (a < b)

Which works because in javascript:

true - true // gives 0
false - false // gives 0
true - false // gives 1
false - true // gives -1

Apply it like this:

array.sort(function(a, b) { 
    return cmp(a.strength,b.strength) || cmp(a.name,b.name)
})

Javascript is really missing Ruby's spaceship operator, which makes such comparisons extremely elegant.

Expand your sort function to be like this;

function sortF(ob1,ob2) {
    if (ob1.strength > ob2.strength) {
        return 1;
    } else if (ob1.strength < ob2.strength) { 
        return -1;
    }

    // Else go to the 2nd item
    if (ob1.name < ob2.name) { 
        return -1;
    } else if (ob1.name > ob2.name) {
        return 1
    } else { // nothing to split them
        return 0;
    }
}

A < and > comparison on strings is an alphabetic comparison.