相关疑难解决方法(0)

请考虑以下内容:(
编辑:我稍微修改了函数以删除三元运算符的使用或括号)

function someFunction(start,end,step){
  var start = start || 1,
      end = end || 100,
      boolEndBigger = (start < end);   // define Boolean here
      step = step || boolEndBigger ? 1:-1;
  console.log(step); 
}

someFunction()
// step isn't defined so expect (1<10) ? 1:-1  to evaluate to 1

someFunction(1,10)  
// again step isn't defined so expect to log 1 as before

问题:

someFunction(1,10,2) 
//step IS defined, shortcut logical OR || should kick in, 
//step should return 2 BUT it returns 1 …

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