How do I update first item of time using map?
const myArr = [{
day: 1,
time: [1200, 1400]
}]
newTime = 1300;
myNewArr = myArr.map(d => {
return {
day: d.day,
time: [newTime] // but this don't care about order
}
})
console.log(myNewArr)
which is 1200, replace it with says 1300, but keep 1400 as the second item? or vice versa replace 1400 with another number.
You could use Object.assign and take an object with the wanted index for replacement.
var myArr = [{ day: 1, time: [1200, 1400] }],
newTime = 1300,
myNewArr = myArr.map(
({ day, time }) => ({ day, time: Object.assign([], time, { 0: newTime }) })
);
console.log(myNewArr);
Considering that you don't want to update the original array, you could use slice with spread syntax to update the data like
const myArr = [{
day: 1,
time: [1200, 1400]
}]
newTime = 1300;
myNewArr = myArr.map(d => {
return {
day: d.day,
time: [newTime, ...d.time.slice(1)]
}
})
console.log(myNewArr)Please note that mapping over your data and updating like above will update the entire list of objects.
You could use Object.assign instead of spread syntax as @NinaScholz also suggested, That way you can update any particular index. It comes from the fact that array accepts integer indices
const myArr = [{
day: 1,
time: [1200, 1400]
}]
newTime = 1300;
myNewArr = myArr.map(d => {
return {
day: d.day,
time: Object.assign([], time, {1: newTime})
}
})
console.log(myNewArr)
time: [newTime, ...d.time.slice(1)] if I want to update the second array instead of the first one?time: [...d.time.slice(0, index), newTime, ...d.time.slice(index + 1)] where index is the index that you want to update, this syntax will work with index 0 as well
assign because of the temporary array).
myArr[0].time[0] = 1300?spreadoperator instead