How do I create a function using reduce which will take in an array of objects and return an object directory with unique keys, but allowing for repeated values?
I would like the output to look like this:
{
Bob: {
'0': { name: 'Bob', age: 30, voted: true },
'1': { name: 'Bob', age: 31, voted: true },
'2': { name: 'Bob', age: 32, voted: true },
},
Jake: {
'0': { name: 'Jake', age: 20, voted: false },
'1': { name: 'Jake', age: 32, voted: true }
},
Phil: { name: 'Phil', age: 21, voted: true },
Ed: { name: 'Ed', age: 55, voted: true },
Tami: { name: 'Tami', age: 54, voted: true },
Mary: { name: 'Mary', age: 31, voted: false },
Becky: { name: 'Becky', age: 43, voted: false },
Joey: { name: 'Joey', age: 41, voted: true },
Jeff: { name: 'Jeff', age: 30, voted: true },
Zack: { name: 'Zack', age: 19, voted: false }
}
This is my code, the results eat one another if two repeated names happen, and it spreads the first object into the key without adding a number key to it.
let count = 0
const toNamedObj = (arr) => {
return arr.reduce((acc, cur) => {
let key = Object.values(cur)[0]
if(acc.hasOwnProperty(key)){
count ++
console.log(count)
return {[key]: {...acc[key], [count]: cur} }
}
return {...acc, [key]: cur}
} ,{})
}
const voters = [
{name:'Bob' , age: 30, voted: true},
{name:'Bob' , age: 31, voted: true},
{name:'Bob' , age: 32, voted: true},
{name:'Jake' , age: 32, voted: true},
{name:'Kate' , age: 25, voted: false},
{name:'Jake' , age: 20, voted: false},
{name:'Phil' , age: 21, voted: true},
{name:'Ed' , age:55, voted:true},
{name:'Tami' , age: 54, voted:true},
{name: 'Mary', age: 31, voted: false},
{name: 'Becky', age: 43, voted: false},
{name: 'Joey', age: 41, voted: true},
{name: 'Jeff', age: 30, voted: true},
{name: 'Zack', age: 19, voted: false}
];
console.log(toNamedObj(voters)); Using your current approach, you'd have to be able to detect, when iterating, if the name already exists, if the object nested in it is a plain voter object (in which case it'd have to be removed and replaced with the array-like object), or if it's the array-like object. While that'd be possible, it'd be convoluted. A better approach would be to unconditionally group into arrays indexed by name, and then transform each array into either the single voter object, or into the {0: .. 1: } object afterwards.
const toNamedObj = (arr) => {
const votersByName = {};
for (const voter of voters) {
votersByName[voter.name] ??= [];
votersByName[voter.name].push(voter);
}
for (const [name, voters] of Object.entries(votersByName)) {
votersByName[name] = voters.length === 1
? voters[0]
: { ...voters };
}
return votersByName;
}
const voters = [
{name:'Bob' , age: 30, voted: true},
{name:'Bob' , age: 31, voted: true},
{name:'Bob' , age: 32, voted: true},
{name:'Jake' , age: 32, voted: true},
{name:'Kate' , age: 25, voted: false},
{name:'Jake' , age: 20, voted: false},
{name:'Phil' , age: 21, voted: true},
{name:'Ed' , age:55, voted:true},
{name:'Tami' , age: 54, voted:true},
{name: 'Mary', age: 31, voted: false},
{name: 'Becky', age: 43, voted: false},
{name: 'Joey', age: 41, voted: true},
{name: 'Jeff', age: 30, voted: true},
{name: 'Zack', age: 19, voted: false}
];
console.log(toNamedObj(voters));Or by mapping the entries
const toNamedObj = (arr) => {
const votersByName = {};
for (const voter of voters) {
votersByName[voter.name] ??= [];
votersByName[voter.name].push(voter);
}
return Object.fromEntries(
Object.entries(votersByName)
.map(([name, voters]) => ([
name,
voters.length === 1 ? voters[0] : { ...voters }
]))
);
}
const voters = [
{name:'Bob' , age: 30, voted: true},
{name:'Bob' , age: 31, voted: true},
{name:'Bob' , age: 32, voted: true},
{name:'Jake' , age: 32, voted: true},
{name:'Kate' , age: 25, voted: false},
{name:'Jake' , age: 20, voted: false},
{name:'Phil' , age: 21, voted: true},
{name:'Ed' , age:55, voted:true},
{name:'Tami' , age: 54, voted:true},
{name: 'Mary', age: 31, voted: false},
{name: 'Becky', age: 43, voted: false},
{name: 'Joey', age: 41, voted: true},
{name: 'Jeff', age: 30, voted: true},
{name: 'Zack', age: 19, voted: false}
];
console.log(toNamedObj(voters));I recommend against using .reduce when the accumulator is the same value on each iteration - a plain for loop is simpler to write and understand.
Presented below is one possible way to achieve the desired objective.
Code Snippet
// method to transform arr to desired format
const toNamedObj = arr => (
arr.reduce(
(acc, {name, voted, ...rest}, idx) => (
(acc[name] ??= []).push({ name, voted, ...rest }),
(idx === arr.length - 1 && Object.entries(acc).forEach(
([k, v]) => (acc[k] = (v.length === 1) ? v[0] : {...v})
)),
acc
),
{}
)
);
/* with explanation
// method to transform arr to desired format
const toNamedObj = arr => (
// iterate using ".reduce()"
arr.reduce(
(acc, {name, voted, ...rest}, idx) => {
// if "name" not present in "acc", set it as empty array
acc[name] ??= [];
// push elt into array
acc[name].push({ name, voted, ...rest });
// when iterating over the last item, special processing
if (idx === arr.length - 1) { // processed last elt in arr
// review each value in "acc" and convert to object
Object.entries(acc)
.forEach(([k, v]) => {
if (v.length === 1) { // only one elt in value-array
// place the elt as-is
acc[k] = v[0];
} else { // multiple elts in val-arr
// convert val-arr to object
acc[k] = {...v};
}
});
};
// always return the accumulator "acc" in ".reduce()" callback
return acc;
},
{} // "acc" is set as an empty object initially
)
);
*/
const voters = [
{name:'Bob' , age: 30, voted: true},
{name:'Bob' , age: 31, voted: true},
{name:'Bob' , age: 32, voted: true},
{name:'Jake' , age: 32, voted: true},
{name:'Kate' , age: 25, voted: false},
{name:'Jake' , age: 20, voted: false},
{name:'Phil' , age: 21, voted: true},
{name:'Ed' , age:55, voted:true},
{name:'Tami' , age: 54, voted:true},
{name: 'Mary', age: 31, voted: false},
{name: 'Becky', age: 43, voted: false},
{name: 'Joey', age: 41, voted: true},
{name: 'Jeff', age: 30, voted: true},
{name: 'Zack', age: 19, voted: false}
];
console.log(toNamedObj(voters));.as-console-wrapper { max-height: 100% !important; top: 0 }Explanation
Inline comments added to the snippet above.