我无法根据 JavaScript [初学者] 中的条件编写 for...in 循环

Question

我正在尝试修改 function 以返回 16 岁或以上的人数。 我知道我需要一个 for...in 循环。 这就是我所得到的。 请帮忙。

function countLegalDrivers(people){

}

const examplePeopleArray = [
  { name: 'John', age: 15},
  { name: 'Jane', age: 16},
  { name: 'Jack', age: 17}
];

console.log(countLegalDrivers(examplePeopleArray), '<-- should be 2');

Answer 1

您也可以使用过滤器或不使用过滤器

 // with filter function countLegalDrivers(people) { return people.filter(p => p.age >= 16).length; } // with ordinary for loop /* function countLegalDrivers(people) { var count = 0; for(var i=0;i<people.length;i++){ if(people[i].age>=16){ count++; } } return count; } */ const examplePeopleArray = [ { name: "John", age: 15 }, { name: "Jane", age: 16 }, { name: "Jack", age: 17 } ]; console.log(countLegalDrivers(examplePeopleArray));

Answer 2

  function countLegalDrivers(people){
  return people.reduce((prev,cur)=>prev+(cur.age>=16?1:0),0);
}

const examplePeopleArray = [
  { name: 'John', age: 15},
  { name: 'Jane', age: 16},
  { name: 'Jack', age: 17}
];

console.log(countLegalDrivers(examplePeopleArray), '<-- should be 2');

Array.prototype.reduce function 很容易解决您的问题。