I have two arrays which are taken in different time periods. How to check what player has gone up/down in the list with the inclusion of marking a new player also as going up?
P.S. - Arrays are already sorted according to the score.
pastData:[
{
playerName:'John Doe',
score:50
},
{
playerName:'Jane Doe',
score:40
},
{
playerName:'John Appleseed',
score:30
},
{
playerName:'John Walker',
score:20
},
]
presentData:[
{
playerName:'Jane Doe',
score:80
},
{
playerName:'John Doe',
score:60
},
{
playerName:'John Appleseed',
score:40
},
{
playerName:'John Mayer',
score:30
},
]
I need to check the index changes comparing the two arrays and get an output like following.
presentData:[
{
playerName:'Jane Doe',
score:80,
position:'up'
},
{
playerName:'John Doe',
score:60,
position:'down'
},
{
playerName:'John Appleseed',
score:40,
position:'same'
},
{
playerName:'John Mayer',
score:30,
position:'up'
},
]
I'm trying as below but can't seem to find a solution for the new player usecase.
let status=[] //this array will include the changes
which I can use later to update the presentData array
with a "position:'up/down/same'" key-value pairs.
for (let i = 0; i < 4; i++) {
for(let j=0; j<4; j++) {
if(Object.values(pastData)[i].id==Object.values(presentData)[j].id){
if(i==j){
status.push('same')
}
if(i<j){
status.push('down')
}
if(i>j){
status.push('up')
}
}
}
}
Create a Map out of the pastData array which maps the playerName to their index.
Iterate over the presentData array and using the map calculate the position for every player.
const pastData = [
{ playerName: "John Doe", score: 50 },
{ playerName: "Jane Doe", score: 40 },
{ playerName: "John Appleseed", score: 30 },
{ playerName: "John Walker", score: 20 },
];
const presentData = [
{ playerName: "Jane Doe", score: 80 },
{ playerName: "John Doe", score: 60 },
{ playerName: "John Appleseed", score: 40 },
{ playerName: "John Mayer", score: 30 },
];
const pastDataMap = new Map(pastData.map((d, i) => [d.playerName, i]));
const status = presentData.map((d, i) => {
const pastIndex = pastDataMap.get(d.playerName);
return {
...d,
position:
pastIndex === undefined || i < pastIndex
? "up"
: i > pastIndex
? "down"
: "same",
};
});
console.log(status);Other relevant documentations:
You can create a pastDataScoreHash with Array.prototype.reduce() and create a result array with Array.prototype.map() adding position property to each players and getting it's value by comparing the pastDataScoreHash's past score with current score
Code:
const pastData = [
{ playerName: 'John Doe', score: 50 },
{ playerName: 'Jane Doe', score: 40 },
{ playerName: 'John Appleseed', score: 30 },
{ playerName: 'John Walker', score: 20 },
]
const presentData = [
{ playerName: 'Jane Doe', score: 80 },
{ playerName: 'John Doe', score: 60 },
{ playerName: 'John Appleseed', score: 40 },
{ playerName: 'John Mayer', score: 30 },
]
const pastDataHash = pastData.reduce((a, { playerName: p }, i) => ((a[p] = i), a), {})
const getPosition = (past, current) => {
switch (true) {
case past == current:
return 'same'
case past == undefined || past > current:
return 'up'
default:
return 'down'
}
}
const result = presentData.map((p, i) => ({
...p,
position: getPosition(pastDataHash[p.playerName], i),
}))
console.log(result)https://stackoverflow.com/questions/72401269/compare-two-arrays-of-player-scores-to-see-who-has-gone-up-down-in-the-list#This is a solution about x4 faster than first one.
presentData.map((present,index)=> {
const pastIndexPostion = pastData.findIndex(t => t.playerName === present.playerName)
if(pastIndexPostion > index || pastIndexPostion===-1){
present.position = 'up'
}else if(pastIndexPostion === index){
present.position = 'same'
}else {
present.position = 'down'
}
return present
})