Give Sibling Elements a Unique Key Attribute lll

JavaScript
1

Tell us what’s happening:
hello .
i have passed this challenge, but i am really confuse with it ?
what is the parameter mean? in the map ,
and the key … what is it , i have never see it…

Your code so far



const frontEndFrameworks = [
  'React',
  'Angular',
  'Ember',
  'Knockout',
  'Backbone',
  'Vue'
];

function Frameworks() {
  const renderFrameworks =frontEndFrameworks.map((a,b)=>{
    return <li key={b}>{a}</li>
  })
  return (
    <div>
      <h1>Popular Front End JavaScript Frameworks</h1>
      <ul>
        {renderFrameworks}
      </ul>
    </div>
  );
};

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36.

Link to the challenge:
https://learn.freecodecamp.org/front-end-libraries/react/give-sibling-elements-a-unique-key-attribute

2

First you should look up how map function works. MDN does a good explanation of it. Basically what it does is a parameter is value and b is index. So you are giving <li key> index numbers and its values inside <li> tags. This you do to dynamically generate a list.