Conditional spread element

问题

const cond = false

const extraInfo = [
  {
    a: 11,
    b: 25
  },
  {
    a: 12,
    b: 34
  },
  {
    a: 1,
    c: 99
  }
]

const userInfo = [
  {
    z: 8
  },
  {
    z: 10
  },
  ...(cond && extraInfo)
]

When cond is true, I want both extra and user info.

When cond is false, only userInfo is needed.

The issue is when cond is false, I get

TypeError: (intermediate value)(intermediate value)(intermediate value)[Symbol.iterator] is not a function

My understanding is that I am not allowed to use a boolean as a spread element, in this case ...false.

But ...( cond ? extraInfo : {} ) doesn't seem to work either.

What is going on?

回答1:

Just make it

...(cond ? extraInfo : [])

Demo with true

var cond = true;

var extraInfo = [
  {
    a: 11,
    b: 25
  },
  {
    a: 12,
    b: 34
  },
  {
    a: 1,
    c: 99
  }
];

var userInfo = [
  {
    z: 8
  },
  {
    z: 10
  },
  ...(cond ? extraInfo : [])
];

console.log( userInfo );

Demo with false

var cond = false;

var extraInfo = [
  {
    a: 11,
    b: 25
  },
  {
    a: 12,
    b: 34
  },
  {
    a: 1,
    c: 99
  }
];

var userInfo = [
  {
    z: 8
  },
  {
    z: 10
  },
  ...(cond ? extraInfo : [])
];

console.log( userInfo );

回答2:

Another way:

cond is true:

var extraInfo = [
  {
    a: 11,
    b: 25
  },
  {
    a: 12,
    b: 34
  },
  {
    a: 1,
    c: 99
  }
]

var cond = true;
var userInfo = [
  {
    z: 8
  },
  {
    z: 10
  },
  ...(cond && extraInfo || [])
]
console.log(userInfo);

cond is false:

var extraInfo = [
  {
    a: 11,
    b: 25
  },
  {
    a: 12,
    b: 34
  },
  {
    a: 1,
    c: 99
  }
]

var cond = false;
var userInfo = [
  {
    z: 8
  },
  {
    z: 10
  },
  ...(cond && extraInfo || [])
]
console.log(userInfo);

回答3:

const extraInfo = [
  {
    a: 11,
    b: 25
  },
  {
    a: 12,
    b: 34
  },
  {
    a: 1,
    c: 99
  }
];
const userInfo = [
  {
    z: 8
  },
  {
    z: 10
  },
];

const cond = true;
let getMyValue = cond ? [].concat(extraInfo, userInfo) : userInfo;

console.log(getMyValue)

回答4:

let getMyValue = cond ? [].concat(extraInfo, userInfo) : userInfo;

let check this

const extraInfo = [
  {
    a: 11,
    b: 25
  },
  {
    a: 12,
    b: 34
  },
  {
    a: 1,
    c: 99
  }
];
const userInfo = [
  {
    z: 8
  },
  {
    z: 10
  },
];

const cond = false;
let getMyValue = cond ? [].concat(extraInfo, userInfo) : userInfo;

console.log(getMyValue)

来源：https://stackoverflow.com/questions/47882784/conditional-spread-element