如何添加到 Javascript 中的函数？

Question

I've been going through a bootcamp, and I can't seem to figure out how to add to a function in Javascript, specifically when I've already placed my return value. For example, this function runs, but if someone said "okay, now if there is no one that matches the studying string, return a message that reads "No matches." Where do I add a new if statement saying "if (newArr.length = 0) {return "No matches.} Desperately needing help on this, and I've got an exam on JS functions tomorrow. Thought I had everything down, until this big ole curveball. Any and all help is greatly appreciated, thank you!

 let people = [{ name: "Nick", studying: "JS", age: "33" }, { name: "Joseph", studying: "JS", age: "137" }, { name: "Jeff", studying: "education", age: "1897374" } ]; function returnArrOfNames(people, string) { let newArr = [] for (let i = 0; i < people.length; i++) { if (people[i].studying === string) { newArr.push(people[i].name) } } return newArr } console.log(returnArrOfNames(people, "JS"));

Answer 1

Before you return newArr you can check it's length and if it's zero return "No matches".

let people = [{
    name: "Nick",
    studying: "JS",
    age: "33"
  },

  {
    name: "Joseph",
    studying: "JS",
    age: "137"
  },

  {
    name: "Jeff",
    studying: "education",
    age: "1897374"
  }
];

function returnArrOfNames(people, string) {
  let newArr = []
  for (let i = 0; i < people.length; i++) {
    if (people[i].studying === string) {
      newArr.push(people[i].name)
    }
  }

  if (newArr.length === 0) {
    return "No matches";
  }

  return newArr
}

console.log(returnArrOfNames(people, "JS"));

Answer 2

edit: I posted the same answer as someone else sorry.

You can just add that if statement outside the for loop. Like this:

let people = [
  {name : "Nick",
  studying : "JS",
  age : "33"},

  {name : "Joseph",
  studying : "JS",
  age : "137"},

  {name : "Jeff",
  studying : "education",
  age : "1897374"}
];

function returnArrOfNames(people, string) {
   let newArr = []
   for (let i = 0; i < people.length; i++) {
      if (people[i].studying === string) {
          newArr.push(people[i].name)
      }
   }
   if (newArr.length == 0){
       return console.log("no matches")
   }

   console.log(newArr);
   return newArr
}


returnArrOfNames(people, "JS")

Answer 3

You can utilize Array prototype's map and filter method to get the result:

 let people = [{ name: "Nick", studying: "JS", age: "33" }, { name: "Joseph", studying: "JS", age: "137" }, { name: "Jeff", studying: "education", age: "1897374" } ]; function returnArrOfNames(people = [], studying) { const NO_MATCHES = 'No Matches' const isEmpty = people.length === 0 if (isEmpty) { return NO_MATCHES } const filterFn = i => i.studying === studying const filteredPeople = people.filter(filterFn) const isEmptyFilteredPeople = filteredPeople.length === 0; if(isEmptyFilteredPeople) return NO_MATCHES const mapFn = i => i.name const mappedPeople = filteredPeople.map(mapFn); return mappedPeople } console.log(returnArrOfNames(people, "JS"));

Good Luck...

Answer 4

the more simple is array.reduce method, and use a ternary condition for return

 const people = [ { name: 'Nick', studying: 'JS', age: '33' } , { name: 'Joseph', studying: 'JS', age: '137' } , { name: 'Jeff', studying: 'education', age: '1897374' } ] function returnArrOfNames(arr, study) { let newArr = arr.reduce((a,c)=> { if (c.studying===study) a.push(c.name) return a }, []) return newArr.length ? newArr : 'no matches' } console.log(' JS ? ->', returnArrOfNames(people, "JS") ) // Array [ "Nick", "Joseph" ] console.log(' xx ? ->', returnArrOfNames(people, "xx") ) // "no matches"

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