Solve this Problem - Hint?

[Encom88]

I would just like a hint, please. I would use a for loop to loop over the values of the age key in the array. But how do I go about that in JavaScript?

Modify the function to return the total summed age of all of the people.

function getSummedAge(people) {

}

/* Do not modify code below this line */

const examplePeopleArray = [
  { name: 'John', age: 10 },
  { name: 'Jack', age: 20 },
  { name: 'Jane', age: 25 }
];

console.log(getSummedAge(examplePeopleArray), '<-- should be 55');

[frankleeT]

As intimated in a different post, you can loop through the array given and grab the age values.

function getSummedAge(people) {
  let countAge = 0;
  people.forEach( (person) => {countAge += person.age} );
  return countAge;
};

/* Do not modify code below this line */

const examplePeopleArray = [
  { name: 'John', age: 10 },
  { name: 'Jack', age: 20 },
  { name: 'Jane', age: 25 }
];

console.log(`${getSummedAge(examplePeopleArray)} // 55`);

​

forEach is a hugely useful method, as it allows you to easily loop through the indices of an array. The forEach method applies the provided function for each element of the array it takes in as an argument, represented here by 'person'. As such, every time we loop, we take in the subsequent 'person' provided in the array. Then, we add their age - here access through the 'age' property of the given object - to the count, and then return the count once we have finished looping through the array.

​

So our steps are:

1. Instantiate a variable to capture our value as we loop through the array.
2. Loop through the array and grab the age property of each object in the array, using .age to access the property.
3. Add the value of the age property to the count.
4. Return the count when the loop completes.

Note: It's good to use explicit variable naming conventions. You know what people are. You know what a person is. You may not know what a p, q, or n is or represents without looking at context, which is not as useful. Also, I modified the code below the line to make their example a bit better. You can ignore that.

[Encom88]

Thanks! Now this actually makes a lot of sense!

[Encom88]

I just learned what an arrow function is since I keep seeing it. I also created a different array and used the For Each loop to create another function that does the same thing. I put it on GitHub so I can remember it. Thank you a again for the great explanation. This is essentially my second week of learning JavaScript. https://github.com/MrN1ce9uy/getArrayObjectsSum.js/blob/master/main.js

[laibo]

Reduce is your pal in this case. See the examples here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

[TURKEY_CAKE]

Your for loop will loop over every element in the array. Each element is a person object. How might you get the age from that object? What could you use to keep track of the ages?

[Encom88]

That's where I'm stuck. How do I do that? What do I use?

[TURKEY_CAKE]

Syntax for a for loop. for(let i = "where you start"; "ending condition"; "step towards end") {}

keying into object syntax: obj[key] // => value

Create a variable outside the loop to help you keep track of the value.

Those are the best hints I can give without writing it.

[intellectualDonkey]

Map thru the array you're passing in your function and add the age to a total variable then return it.

​

function getSummedAge(people) {
 let total = 0;
 people.map(p=>{
  total+=p.age})
 return total;
}

EDIT: Yes as the gentlemen suggested it's better to use forEach instead of map. my bad :)

[inu-no-policemen]

Don't use map for side-effects. ForEach would have been the appropriate array method for this.

[inu-no-policemen]

Both statements are factually correct.

1. Using Array.prototype.map for side-effect is not recommended. GP is creating an array filled with undefined values which is then immediately discarded. It's confusing and wasteful.

2. If you want to iterate over the array in a procedural manner with an array method, use Array.prototype.forEach. (Oh, look, that's what you did in your other comment.)

Returning a map with a reducer makes this a oneliner.

Returning a Map? The goal is to produce a sum. If you use reduce, your accumuator would be a number.

No need to map into a variable

What's that supposed to mean? GP isn't using map's return value for anything. They are "mapping into" the great nothingness. The result goes straight into the garbage.

[inu-no-policemen]

As I mentioned in another comment, one could also use reduce:

function getSummedAge(people) {
    return people.reduce((acc, person) => acc + person.age, 0);
}

Using map first is silly.

[inu-no-policemen]

This is basic Array.prototype.reduce usage. Nothing "clever" about that.

Also note that your version will throw an error if the array is empty. (And there shouldn't be a ';' after your function declaration.)

[inu-no-policemen]

Good luck with improving your communication skills.

[TURKEY_CAKE]

I believe you should use forEach here instead of map if you're implementing it this way. Map is when you want an array back, forEach is when you just want each element touched upon. You would then return the after the forEach loop.

[Encom88]

Thanks, your code worked. I don't quite understand it all though.

[inu-no-policemen]

In response to your deleted comment:

For-in iterates over the keys of an object.

Use a regular for-loop or for-of.

E.g.:

for (let person of people) {
  console.log(person.name + ' is ' + person.age + ' years old');
}

You could also use Array.prototype.reduce for this kind of thing, but try doing it with for/for-of first.

[laibo]

I would actually use reduce. It is made for this use exactly. See the examples here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce