cycle background colors

primary-colors.js

$(function () {
    
    function tick (str) {
      indexs[str] = (indexs[str] + 1) % arrays[str].length
      return arrays[str][indexs[str]]
    }
    
    var arrays = {}
    arrays.colors = [
      'yellow',
      'red',
      'blue'
    ]
    
    var indexs = {}
    indexs.colors = 0
    
    function draw() {
        $('body').css({
            background: tick('colors')
        })
    }
    
    setInterval(draw, 250)

})