I have an array of objects, and according to a property inserted in one of them i would like to mark or select all the objects previous to that object container of the specific property
My array is in this way:
const arrX= [
{ status: '1' },
{ status: '2'},
{ status: '3', imHere: true },
{ status: '4' },
];
Then due to the property imHere on arrX[2], the positions arrX[0] and arrX[1] should be modified.
My expected result would be :
const arrX= [
{ status: '1',wasHere:true },
{ status: '2',wasHere:true},
{ status: '3', imHere: true },
{ status: '4' },
];
I know that the map method would be quite useful in this case, but can´t find the way to check from index of object containing imHere backwards the former positions
One approach is to use .findIndex() and .map():
const arrX= [{ status: '1' }, { status: '2'}, { status: '3', imHere: true }, { status: '4'}];
const imHereIndex = arrX.findIndex(({imHere}) => imHere === true);
const result = arrX.map((val, index) => index < imHereIndex
? { ...val, wasHere: true }
: val
);
console.log(result);Even if @Kinglish answer works like a charm I want to share another way to achieve your goal. This road is surely longer than Kinglish ones, never then less is a good alternative.
{ status: '4' },
];
function findProperty(arr) {
const hasProperty = arr.findIndex(el => Object.keys(el).includes('imHere'))
const addNewProperty = arr.map((el,i) => (i < hasProperty) ? {...el, wasHere: true} : el)
return addNewProperty
}
const updatedArray = findProperty(arrX)
console.log(updatedArray)
Here's one method for it using Array#reduce and a boolean to track whether we've encountered inHere
const arrX = [
{status: '1'},
{status: '2'},
{status: '3',imHere: true},
{status: '4'},
];
let found = false,
updated = arrX.reduce((b, a) => {
found = found || (a.hasOwnProperty('imHere') && a.imHere === true)
if (!found) a.wasHere = true;
return b.concat(a);
}, [])
console.log(updated)