Q:

How to get children type in react

I'm trying to make my own Tabs component, so that I can use tabs in my app. However I seem to be having issues trying to extract the child components I need by type. 
import React from 'react'

export class Tabs extends React.Component {
  render() {
    let children = this.props.children
    let tablinks = React.Children.map(children, x => {
      console.log(x.type.displayName) // Always undefined
      if (x.type.displayName == 'Tab Link') {
        return x
      }
    })

    return (
      <div className="tabs"></div>
    )
  }
}

export class TabLink extends React.Component {
  constructor(props) {
    super(props)
    this.displayName = 'Tab Link'
  }
  render() {
    return (
      <div className="tab-link"></div>
    )
  }
}

<Tabs>
    <TabLink path="tab1">Test</TabLink>
    <TabLink path="tab2">Test2</TabLink>
</Tabs>

My console.log never returns "Tab Link", it always returns undefined, why?

A:

As an alternative you could use
console.log(x.type.name) // this would be 'TabLink'

You don't need to explicitly define displayName in this case.
https://jsfiddle.net/lustoykov/u1twznw7/1/

A:

It's undefined because displayName should be a static property.
class TabLink extends React.Component { 
  constructor(props) {
    super(props)
  }
  render() {
    return (
      <div className="tab-link"></div>
    )
  }
} 
TabLink.displayName = 'Tab Link'

jsfiddle (check the console)

