let data = [
{firstName: 'John', lastName: 'Doe'},
{firstName: 'Mike', lastName: 'Smith'}
]
console.log(data)I want to transform this into one object like this
obj = {firstName: ['John', 'Mike'], lastName: ['Doe', 'Smith']}
should I use reduce?
A generic solution with Array#reduce method.
let result = data.reduce((obj, o) => {
// get all keys of object
Object.keys(o)
// iterate over the keys
.forEach(k => {
// define property if not defined
obj[k] = obj[k] || [];
// push the value to the array
obj[k].push(o[k]);
})
// return object
return obj;
// set initial value as an object for result
}, {})
let data = [{
firstName: 'John',
lastName: 'Doe'
},
{
firstName: 'Mike',
lastName: 'Smith'
}
]
let result = data.reduce((obj, o) => {
Object.keys(o)
.forEach(k => {
obj[k] = obj[k] || [];
obj[k].push(o[k]);
})
return obj;
}, {})
console.log(result)You can use reduce to create a new version of the object.
The reduce() method executes a reducer function (that you provide) on each member of the array resulting in a single output value.
With reduce, we first pass in a function that executes on each item and returns a new output value, then we pass a second parameter defining the initial structure of the single output value.
let data = [
{firstName: 'John', lastName: 'Doe'},
{firstName: 'Mike', lastName: 'Smith'}
]
// o = the current output value
// i = the current item in the array
let result = data.reduce((o, i) => {
// Add the first/last names to the corresponding array
o.firstName.push(i.firstName)
o.lastName.push(i.lastName)
// Return the new current output value
return o
}, { firstName: [], lastName: [] }) // Sets the initial output value
console.log(result)
let data = [
{firstName: 'John', lastName: 'Doe'},
{firstName: 'Mike', lastName: 'Smith'}
]
var firstName = [];var lastName = [];
data.forEach(function(item){
firstName.push(item.firstName);
lastName.push(item.lastName);
})
let obj = {};
obj.firstName = firstName;
obj.lastName = lastName;
let dataModified = [];
dataModified.push(obj);
console.log(dataModified);Here's a single iteration, functional, non-mutating solution:
let data = [
{firstName: 'John', lastName: 'Doe'},
{firstName: 'Mike', lastName: 'Smith'}
]
let result = data.reduce((res, {firstName, lastName}) => ({
firstName: [firstName, ...res.firstName],
lastName: [lastName, ...res.lastName]
}), {firstName: [], lastName: []})
console.log(result)You can also make the logic more generic, irrespective of the properties known
let data = [{
firstName: 'John',
lastName: 'Doe'
},
{
firstName: 'Mike',
lastName: 'Smith'
}
]
let result = data.reduce((o, i) => {
for (const key in i) {
if (!o[key]) {
o[key] = [];
}
o[key].push(i[key]);
}
return o
}, {})
console.log(result)Another simple thing we can do is to call map two times, once on the first names, and once on the last names.
let data = [
{firstName: 'John', lastName: 'Doe'},
{firstName: 'Mike', lastName: 'Smith'}
]
let result = {
firstName: data.map(i => i.firstName),
lastName: data.map(i => i.lastName)
}
console.log(result)