dist/vue.runtime.common.js
function simpleNormalizeChildren (children) {
  for (var i = 0; i < children.length; i++) {
    if (Array.isArray(children[i])) {
      return Array.prototype.concat.apply([], children)
    }
  }
  return children
}
function simpleNormalizeChildren (children) {
  for (var i = 0; i < children.length; i++) {
    if (Array.isArray(children[i])) {
      return Array.prototype.concat.apply([], children)
    }
  }
  return children
}
function simpleNormalizeChildren ( children ) { for ( var i = 0 ; i < children . length ; i ++ ) { if ( Array . isArray ( children [ i ] ) ) { return Array . prototype . concat . apply ( [ ] , children ) } } return children }
1. When the children contains components - because a functional component may return an Array instead of a single root. In this case, just a simple normalization is needed - if any child is an Array, we flatten the whole thing with Array.prototype.concat. It is guaranteed to be only 1-level deep because functional components already normalize their own children.
1 . When the children contains components - because a functional component may return an Array instead of a single root . In this case just a simple normalization is needed - if any child is an Array we flatten the whole thing with Array . prototype . concat . It is guaranteed to be only 1 - level deep because functional components already normalize their own children .