小编Ale*_*x P的帖子

有什么功能之间的差异doall,dorun,doseq,和for？

我发现一些信息散布在整个互联网上,但我认为最好将这些信息集中在这里.

我正在阅读Eloquent Javascript这本书,我正在做一个练习,我很难理解我做错了什么.以下是正确计算平均值的代码(祖先是JSON对象):

function average(array) {
  function plus(a, b) { return a + b; }
  return array.reduce(plus) / array.length;
};

function age(p) { return p.died - p.born; };

function groupBy(array, action){
  var groups = {};
  array.forEach(function(individual){
    var group = action(individual);
    if (groups[group] == undefined)
      groups[group] = [];
    groups[group].push(individual);
  });
  return groups;
};

var centuries = groupBy(ancestry, function(person){
  return Math.ceil(person.died / 100);
});

console.log(average(centuries[16].map(age)));
console.log(average(centuries[17].map(age)));
console.log(average(centuries[18].map(age)));
console.log(average(centuries[19].map(age)));
console.log(average(centuries[20].map(age)));
console.log(average(centuries[21].map(age)));
// ? 16: 43.5
//   17: 51.2
//   18: 52.8
//   19: 54.8 …