I need to generate an enumErrorList like this
Errors={
none:0,
subject:1,
content:2,
sender:4,
recipient:8
}
from an array like this
let errors=[
'none',
'subject',
'content',
'sender',
'recipient'
]
but I’m sorry I’m not very familiar with enum.
Use Object.entries and Object.fromEntries as follows
let errors=[
'none',
'subject',
'content',
'sender',
'recipient'
]
let Errors = Object.fromEntries(Object.entries(errors).map(([a,b]) => [b, ((1<<a)>>1)]));
console.log(Errors)
|0. I was wracking my brain trying to figure out how to make it with bitwise operations only since 1 << index was the correct way...aside from 0. For some reason I completely forgot I ignored I could just use two operations. Your /2 reminded me of that, so it finally clicked 1 << index >> 1 to only set bit n-1 which happens to be no bits for index = 0.
You can take the array then use Array#reduce and Object.assign to generate an object there where:
let errors=[
'none',
'subject',
'content',
'sender',
'recipient'
]
const Errors = errors.reduce(
(acc, item, index) => Object
.assign(
acc,
{[item]: Math.floor(2 ** (index - 1))}
),
{}
)
console.log(Errors)Or via bit arithmetic to only produce powers of 2 by setting bit n-1 starting with 0 when n=0:
let errors=[
'none',
'subject',
'content',
'sender',
'recipient'
]
const Errors = errors.reduce(
(acc, item, index) => Object
.assign(
acc,
{[item]: (1 << index) >> 1}
),
{}
)
console.log(Errors)