typeof (xb): object
xb === yb: true
xb !== zb: true
xb == true: true
xb === true: false
xb.foob: 3
typeof (xn): object
xn === yn: true
xn !== zn: true
xn == 5: true
xn === 5: false
xn.foon: 3
typeof (xs): object
xs === ys: true
xs !== zs: true
xs == 'bob': true
xs === 'bob': false
xs.foos: 3