This is my array:
[{
name: "Test",
skills: {
agile: true,
good: true
}
},
{
name: "Test 2",
skills: {
agile: false,
good: false
}
}]
I need to find the last element (his index) who has the skill good set to true. The only way I know to fix this is to use a for/if combination. Is there any other faster/optimal way to do it ?
Use filter:
const goodSkills = myArray.filter(x => x.skills.good)
Then get the last item:
goodSkills[goodSkills.length - 1]
Or if you only need the index, and we treat name as a unique key:
const lastGoodIndex = myArray.findIndex(x => x.name === goodSkills[goodSkills.length - 1].name)
You can then use lastGoodIndex for whatever nefarious purpose you have in mind.
Alternatively if name is not a unique key, I suggest just using forEach:
let lastGoodIndex;
myArray.forEach((x, i) => lastGoodIndex = x.skills.good ? i : lastGoodIndex);
console.log(lastGoodIndex);
myArray.forEach((x, i) => lastGoodIndex = x.skills.good ? i : lastGoodIndex) and ditch filter completely (as nice as it is).The fastest way is to us a for loop:
var arr = [{
name: "Test",
skills: {
agile: true,
good: true
}
},
{
name: "Test 2",
skills: {
agile: false,
good: false
},
}]
function findLastGoodIndex(arr) {
for (let i = arr.length - 1; i >= 0; i--) {
if (arr[i].skills.good) {
return i;
}
}
}
console.log(findLastGoodIndex(arr));Or if the list isn't that large you can combine reverse with findIndex:
arr.reverse().findIndex(x => x.skills.good));
skills.good as static check killed the idea. Hence went with plain old whileYou can do it in 3 rows:
var arr = [
{
name: "Test",
skills: {
agile: true,
good: true
}
},
{
name: "Test 2",
skills: {
agile: false,
good: false
},
}
]
var lastIndex;
arr.forEach(function(item, i) {
if(item.skills.good) lastIndex = i;
})
console.log(lastIndex);If you want the index of last element that has good = true your best option is to use for/if (perhaps going backwards, i.e. i-- if you can guess where can you expect the good item?).
filter will find the item(s) too, and it also has index property, but generally it's slower than for/if.
forEach will also generally be slower than for/if.
edit:styling.
Since you need to search the last value, you should search in descending order. This would prevent any unnecessary iterations.
var data = [{
name: "Test",
skills: {
agile: true,
good: true
}
},
{
name: "Test 2",
skills: {
agile: false,
good: false
}
}
];
var i = data.length;
var result = null;
while (i--) {
if (data[i].skills.good) {
result = i;
break;
}
}
console.log(result);