I want to create object of arrays but when i run below code it gives
TypeError: Cannot read property 'push' of undefined
How can i push something to not existing array?
const obj = {}
someArray.forEach(key => {
anotherArray.forEach(key2 => {
obj[key].push(key2)
})
})
Here obj is an empty array , it does not have key property. So before pushing you can check if it has the property , if not then you can create and then push
const obj = {}
someArray.forEach(key => {
anotherArray.forEach(key2 => {
if (!obj[key]) {
obj[key] = []
}
obj[key].push(key2)
})
})