My attempt on getting equilibrium index in an array

eia.js

function sol(A) {
    var eia = A.length,
        addLeft = 0,
        addRight = 0;
    
    for(var i=0; i<eia; i++) {
        addRight += A[i]
    }
    
    for(var i=0; i<eia; i++) {
        addRight -= A[i];
        if(addRight == addLeft) {
            return i;
        }
        addLeft += A[i];
    }
    return -1; 
}