Why I can't call this function for each array item?

Question

I got these 2 arrays and I would like to have a function (randomize() in this case) to be applied to each of them by calling the function and outputing the result to the console. Currently the console.log returns undefined

const array1 = ['I want to','You want to'];
let newArray1 = array1
            .map(item => ({value: Math.random(), item:item}))
            .sort((a,b)=> a.value-b.value)
            .map(item => item.item)
            .slice(0,1);



const array2 = [' eat',' sleep '];
let newArray2 = array2
                .map(item => ({value: Math.random(), item:item}))
                .sort((a,b)=> a.value-b.value)
                .map(item => item.item)
                .slice(0,1);


randomize = (x) =>{
  x.map(item => ({value: Math.random(), item:item}))
  .sort((a,b)=> a.value-b.value)
  .map(item => item.item)
  .slice(0,1);

}
randomize(array2);


console.log(randomize(array2));

Mark_M, I edited the code shortly after I posted. it should have been array2 — KT-mongo, Mar 28 '18 at 19:25

score 4 · Accepted Answer · answered Mar 28 '18 at 19:10

4

You are missing the return statement in your randomize function

randomize = (x) =>{
  return x.map(item => ({value: Math.random(), item:item}))
  .sort((a,b)=> a.value-b.value)
  .map(item => item.item)
  .slice(0,1);  
}

answered Mar 28 '18 at 19:10

Moti Korets

3,738
2
26
35

score 2 · Answer 2 · answered Mar 28 '18 at 19:10

randomize is an arrow function with no return value. Either add a return statement or remove the curly braces to use the implicit return for arrow function's whose body only includes an expression.

const randomize = (x) => {
  return x.map(item => ({value: Math.random(), item:item}))
  .sort((a,b)=> a.value-b.value)
  .map(item => item.item)
  .slice(0,1);
}

or:

const randomize = (x) => 
  x.map(item => ({value: Math.random(), item:item}))
  .sort((a,b)=> a.value-b.value)
  .map(item => item.item)
  .slice(0,1)
;

Also, in case randomize hasn't been declared anywhere, I added the const keyword to avoid creating an implicit global.

score -1 · Answer 3 · answered Mar 28 '18 at 19:18

-1

you are missing return in map function

const array2 = [' eat',' sleep '];

randomize = (x) =>{
  x.map(item => { return {value: Math.random(), item:item}})
  .sort((a,b)=> a.value-b.value)
  .map(item =>return  item.item)
  .slice(0,1);

}

randomize(array2);

answered Mar 28 '18 at 19:18

Arash

3,458
7
32
50

adding unnecessary returns in the map functions will not make the containing function return a value. the other provided solutions are correct. – derelict Mar 28 '18 at 19:39

Why I can't call this function for each array item?

3 Answers3