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)
    })
})

CodePudding user response：

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)
  })
})

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