How can I use comments inside the render
method in a React component?
I have the following component:
'use strict';
var React = require('react'),
Button = require('./button'),
UnorderedList = require('./unordered-list');
class Dropdown extends React.Component{
constructor(props) {
super(props);
}
handleClick() {
alert('I am click here');
}
render() {
return (
<div className="dropdown">
// whenClicked is a property not an event, per se.
<Button whenClicked={this.handleClick} className="btn-default" title={this.props.title} subTitleClassName="caret"></Button>
<UnorderedList />
</div>
)
}
}
module.exports = Dropdown;
My comments are showing up in the UI.
What would be the right approach to apply single and multiple line comments inside a render method of a component?
This question is related to
reactjs
react-native
{
// any valid js expression
}
If you wonder why does it work? it's because everything that's inside curly braces { } is a javascript expression,
so this is fine as well:
{ /*
yet another js expression
*/ }
To summarize, JSX doesn't support comments, either html-like or js-like:
<div>
/* This will be rendered as text */
// as well as this
<!-- While this will cause compilation failure -->
</div>
and the only way to add comments "in" JSX is actually to escape into JS and comment in there:
<div>
{/* This won't be rendered */}
{// just be sure that your closing bracket is out of comment
}
</div>
if you don't want to make some nonsense like
<div style={{display:'none'}}>
actually, there are other stupid ways to add "comments"
but cluttering your DOM is not a good idea
</div>
Finally, if you do want to create a comment node via React, you have to go much fancier, check out this answer.
Here is another approach that allows you to use //
to include comments:
return (
<div>
<div>
{
// Your comment goes in here.
}
</div>
{
// Note that comments using this style must be wrapped in curly braces!
}
</div>
);
The catch here is you cannot include a one-line comment using this approach. For example, this does not work:
{// your comment cannot be like this}
because the closing bracket }
is considered to be part of the comment and is thus ignored, which throws an error.
1) // (Double Forward Slash) is used to comment only single line in react native code but it can only be used outside of the render block. If you want to comment in render block where we use JSX you need to use the 2nd method.
2) If you want to comment something in JSX you need to use JavaScript comments inside of Curly braces like {/comment here/}. It is a regular /* Block Comments */, but need to be wrapped in curly braces.
shortcut keys for /* Block Comments */:
Ctrl + / on Windows + Linux.
Cmd + / on macOS.
JSX Comments Syntax: You can use
{/**
your comment
in multiple lines
for documentation
**/}
or
{/*
your comment
in multiple lines
*/}
for multiple lines comment. And also,
{
//your comment
}
for single line comment.
Note: The syntax:
{ //your comment }
doesn't work. You need to type braces in new lines.
Curly braces are used to distinguish between JSX and JavaScript in a React component. Inside curly braces, we use JavaScript comment syntax.
Reference: click here
Besides the other answers, it's also possible to use single line comments just before and after the JSX begines or ends. Here is a complete summary:
(
// this is a valid comment
<div>
...
</div>
// this is also a valid comment
/* this is also valid */
)
If we were to use comments inside the JSX rendering logic:
(
<div>
{/* <h1>Valid comment</h1> */}
</div>
)
When declaring props single line comments can be used:
(
<div
className="content" /* valid comment */
onClick={() => {}} // valid comment
>
...
</div>
)
When using single line or multiline comments inside the JSX without wrapping them in { }
, the comment will be rendered to the UI:
(
<div>
// invalid comment, renders in the UI
</div>
)
JavaScript comments in JSX get parsed as Text and show up in your app.
You can’t just use HTML comments inside of JSX because it treats them as DOM Nodes:
render() {
return (
<div>
<!-- This doesn't work! -->
</div>
)
}
JSX comments for single line and multiline comments follows the convention
Single line comment:
{/* A JSX comment */}
Multiline comments:
{/*
Multi
line
comment
*/}
According to the official site. These are the two ways
<div>
{/* Comment goes here */}
Hello, {name}!
</div>
Second Example:
<div>
{/* It also works
for multi-line comments. */}
Hello, {name}!
</div>
Here is the link: https://reactjs.org/docs/faq-build.html#how-can-i-write-comments-in-jsx
{/*_x000D_
<Header />_x000D_
<Content />_x000D_
<MapList />_x000D_
<HelloWorld />_x000D_
*/}
_x000D_
On the other hand, the following is a valid comment, pulled directly from a working application:
render () {
return <DeleteResourceButton
//confirm
onDelete={this.onDelete.bind(this)}
message="This file will be deleted from the server."
/>
}
Apparantly, when inside the angle brackets of a JSX element, the //
syntax is valid, but the {/**/}
is invalid. The following breaks:
render () {
return <DeleteResourceButton
{/*confirm*/}
onDelete={this.onDelete.bind(this)}
message="This file will be deleted from the server."
/>
}
According to React's Documentation, you can write comments in JSX like so:
One-line Comment:
<div>
{/* Comment goes here */}
Hello, {name}!
</div>
Multi-line Comments:
<div>
{/* It also works
for multi-line comments. */}
Hello, {name}!
</div>
This is how.
Valid:
...
render() {
return (
<p>
{/* This is a comment, one line */}
{// This is a block
// yoohoo
// ...
}
{/* This is a block
yoohoo
...
*/
}
</p>
)
}
...
Invalid:
...
render() {
return (
<p>
{// This is not a comment! oops! }
{//
Invalid comment
//}
</p>
)
}
...
Source: Stackoverflow.com