var touch1 = function(){
  document.querySelector(‘body‘).addEventListener(‘touchmove‘, function (e) { 
    e.preventDefault(); 
  });
}

var touch2 = function () {
  var lastY;//最后一次y坐标点
  var betterY;//每次touch最高点
  document.querySelector(‘body‘).addEventListener('touchstart', function(event) {
    lastY = event.originalEvent.changedTouches[0].clientY;
    betterY = lastY;
  });
  document.querySelector(‘body‘).addEventListener('touchmove', function(event) {
    var y = event.originalEvent.changedTouches[0].clientY;
    if(y > betterY){
      betterY = y;
    }
    var st = document.body.scrollTop; //滚动条高度
    if (y >= lastY && st <= 10) {
      lastY = y;
      event.preventDefault();
    }
    lastY = y;
  });
  document.querySelector(‘body‘).addEventListener('touchend', function(event) {
    var y = event.originalEvent.changedTouches[0].clientY;
    var st = document.body.scrollTop; //滚动条高度
    if(y < betterY && st <= 10){
      event.preventDefault();
    }
  });
}

var touch3 = function () {
  window.onscroll = function () {
    var top = document.documentElement.scrollTop || document.body.scrollTop;
    if(top <= 0){
      document.body.scrollTop = 0;
    }
  }
}