String Symmetry

stringsymmetry.js

function symmetryPoint ( S ) {
    var length = S.length;
    
    if(length === 1)
        return 0;
    if(length % 2 === 0)
        return -1;
        
    var midpoint = Math.floor(length / 2);
    var fString = S.substring(0, midpoint);
    var lString = S.substring(midpoint + 1, length).split('').reverse('').join('');
    
    if(fString === lString)
        return midpoint;
    else
        return -1;
}