How do i use for loops with react? [duplicate]

问题

This question already has answers here:

Loop inside React JSX (61 answers)

How to loop and render elements in React.js without an array of objects to map? (5 answers)

for loop in react (1 answer)

Closed 2 years ago.

I'm very new to react and all I really want is a simple for loop that creates menuitem elements for each user in my array with the title of it being their firstname. So this is how I would write it, but I have no clue of how to do this in react. I think it should be with a map maybe but I cant seem to get it to work either hopefully anyone out here can help me.

for (var i = 0; i < Users.length; i++) {
  <MenuItem eventKey=[i]>User.firstname[i]</MenuItem>
}

回答1:

The render method of your component, or your stateless component function, returns the elements to be rendered.

If you want to use a loop, that's fine:

render() {
    let menuItems = [];
    for (var i = 0; i < Users.length; i++) {
        menuItems.push(<MenuItem eventKey=[i]>User.firstname[i]</MenuItem>);
    }
    return <div>{menuItems}</div>;
}

More common would be to see a more functional style, such as using a map to return the array of elements:

render() {
    return <div>
    {
        Users.map((user, i) =>
            <MenuItem eventKey=[i]>User.firstname[i]</MenuItem>)
    }
    </div>;
}

Note that in either case, you are missing the key property from each element of your array, so you will see warnings. Each element in an array should have a unique key, preferably some form of ID rather than just the array index.

回答2:

With map you can do:

Users.map((user, index) => (
  <MenuItem eventKey={index}>user.firstname</MenuItem>
));

来源：https://stackoverflow.com/questions/46908480/how-do-i-use-for-loops-with-react