取余运算在模式选择中的运用

var mode = { 0: 'sequence', 1: 'loop', 2: 'random' }
var m = 1
function changeMode() {
    var newMode = (m  + 1) % 3
    console.log(mode[newMode])
    m++
}

changeMode()  // random
changeMode()  // sequence
changeMode()  // loop
changeMode()  // random