实现if(a == 1 && a == 2 && a == 3)为true

function getExpressionTrue() {
    var a = {
        i: 1,
        toString: function() {
            return a.i++
        }
    }
    if(a == 1 && a == 2 && a == 3) {
        console.log('success')
    }
}