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Start your free trialMichael Cook
Full Stack JavaScript Techdegree Graduate 28,975 PointsMy approach to updating score
As it says in the notes for this video, updating a player's score by changing state directly is not a good idea. Before I took any React courses I did the tutorial on the React website and it talks a lot about the importance of immutability: you don't want to change your data directly. Instead you want to replace the old state with a new state that reflects the desired changes. This is my handleScoreChange
method:
/**
* Update a player's score
* @param {Number} delta - change in score
* @param {Number} i - index of player
*/
handleScoreChange = (i, delta) => {
this.setState((prevState) => ({
score: prevState.players.map((player, index) => {
if (i === index) {
player.score += delta
return player
} else {
return player
}
}),
}))
}
I just simply map over the previous state and update the score where the player object's index matches the index passed as an argument, else just return an identical copy of the object. Using map
returns a new array, so it keeps your data immutable. In my opinion this is the easiest and most elegant way and I just wanted to share it.
1 Answer
Zimri Leijen
11,835 PointsYou can simplify it a little, it doesn't need the else block.
handleScoreChange = (i, delta) => {
this.setState((prevState) => ({
score: prevState.players.map((player, index) => {
if (i === index) {
player.score += delta
}
return player
}),
}))
}
Michael Cook
Full Stack JavaScript Techdegree Graduate 28,975 PointsMichael Cook
Full Stack JavaScript Techdegree Graduate 28,975 PointsGood point, thanks.