How do I get a new array from a specific array?
I don't known how to handle an Array like this:
let arr1 = [
{name: 'a', age: 1},
{name: 'a', age: 2},
{name: 'a', age: 3},
{name: 'b', age: 1},
{name: 'b', age: 2}
{name: 'b', age: 3}
{name: 'c', age: 1}
{name: 'c', age: 2}
...
]
"I want this result: from each item with the same name
, pick biggest age
value"
let arr2 = [
{name: 'a', age: 3},
{name: 'b', age: 3},
{name: 'c', age: 2}
...
]
Just use filter
to select all items with the highest age
for their name
.
let arr1 = [{name:'a',age:1},{name:'a',age:2},{name:'a',age:3},{name:'b',age:1},{name:'b',age:2},{name:'b',age:3}]; const biggest = arr1.reduce((a, { name, age }) => { a[name] = a[name] || age; age > a[name] ? a[name] = age : a[name]; return a; }, {}); let arr2 = arr1.filter(({ name, age }) => biggest[name] == age); console.log(arr2);
.as-console-wrapper { max-height: 100% !important; top: auto; }
You can use a combination of reduce
and Object.values
const arr1 = [ {name: 'a', age: 1}, {name: 'a', age: 2}, {name: 'a', age: 3}, {name: 'b', age: 1}, {name: 'b', age: 2}, {name: 'b', age: 3}, {name: 'c', age: 1}, {name: 'c', age: 2}, ] const maxNames = arr1.reduce((maxNamesObject, item) => { const { name, age } = item const maxItem = maxNamesObject[name] if (!maxItem || age > maxItem.age) { maxNamesObject[name] = item } return maxNamesObject }, {}) const output = Object.values(maxNames) console.log(output)
Extracted from this answer: How to filter object array based on attributes?
You can use the Array.prototype.filter
method:
let arr2 = arr1.filter(function (obj) {
return obj.age === 3;
});
This is a more beautiful solution:
let arr1 = [ {name: 'a', age: 1}, {name: 'a', age: 2}, {name: 'a', age: 3}, {name: 'b', age: 1}, {name: 'b', age: 2}, {name: 'b', age: 3}, {name: 'c', age: 1}, {name: 'c', age: 2}, ] arr2 = Array.from(new Set(arr1.map(e => e.name))).map(e => { return { name: e, age: Math.max(...arr1.filter(ee => ee.name == e).map(ee => ee.age)) } }) console.log(arr2)
Blockquote
my solution:
const arr1 = [ {name: 'a', age: 1}, {name: 'a', age: 2}, {name: 'a', age: 3}, {name: 'b', age: 1}, {name: 'b', age: 2}, {name: 'b', age: 3}, {name: 'c', age: 1}, {name: 'c', age: 2}, ] let arr2 = arr1.reduce((acc, item) => { let objectExists = acc.find(e => e.name === item.name) if (!objectExists) acc.push(item) else if (objectExists.age < item.age) { acc[acc.indexOf(objectExists)].age = item.age } return acc }, []) console.log(arr2)
I didn't notice you update the question. This is not the most pro code.
let arr1 = [ {name: 'a', age: 1}, {name: 'a', age: 2}, {name: 'a', age: 3}, {name: 'b', age: 1}, {name: 'b', age: 2}, {name: 'b', age: 3}, {name: 'c', age: 1}, {name: 'c', age: 2} ]; let names = []; let output = []; for(obj of arr1){ if (!names.includes(obj.name)) names.push(obj.name); } for(obj of names){ let current = arr1.filter(x => x.name === obj) .reduce((a,b) => a.age > b.age ? a : b); output.push(current); } console.log(output);
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.