男女比例

gistfile1.js

var _ = require('lodash');

var families = [];

for (var i = 0; i < 100000; i++) {
  var family = [];
  for (var j = 0; j < 3; j++ ) {
    // 0 是女孩  1 是男孩
    var gender = Math.random() >= 0.5 ? 1 : 0;
    family.push(gender);
  }
  families.push(family);
}

var thirds = [];
families.forEach(function (family) {
  if (family[0] === 0 && family[1] === 0) {// 前两胎都是女孩
    thirds.push(family[2]);
  }
});


var result = _.countBy(thirds, function (gender) {
  return gender;
});

console.log(result); // { '0': 12498, '1': 12585 }