Errors and Known Issues for Learning React

programming
1

A great combination of editors and reviewers help ensure that the book's content is error-free. Sometimes, errors do slip through, and this page calls them out. Do note that we fix these errors in subsequent printings, so you may not run into all of the errors listed below.

This is a companion discussion topic for the original entry at https://www.kirupa.com/react/errata.htm
2

Minor error in the web edition, Chapter 11, in the “See the Lifecycle Methods in Action” section, the URL to the example is rendered with a space. Here’s the original:
https://www.kirupa.com/react/ lifecycle_example.htm
And here’s how it should be:
https://www.kirupa.com/react/lifecycle_example.htm

1 Like
3

Thanks for pointing it out. I have updated it on the errata location: Errors and Known Issues for Learning React :slight_smile:

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4

Minor error in the printed version of the book.
The example on page 263 contains a semicolon to much

return {
   countValue: state.count;
}

@kirupa, thanks for the great book!

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6

i have problem in chapter 9

my code:

`<! DOCTYPE html>

<meta charset="utf-8">

<title>От данных к интерфейсу</title>

<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/[email protected]/babel.min.js"></script>

<style>
	#container {
		padding: 50px;
		background-color: #FFF;
	}
</style>

<script type="text/babel">
	var destination = document.querySelector("#container");
	var colors = ["#393E41", "#E94F37", "#1C89BF", "#A1D363", "#85FFC7", "#297373", "#FF8552", "#A40E4C"];

	var renderData = [];

	for (var i = 0; i < colors.length; i++) {
		var color = colors[i];
		renderData.push(<Circle key={i + color} bgColor={color} />);
	}

		

	class Circle extends React.Component {


		render() {
			var circleStyle = {
				padding: 10,
				margin: 20,
				display: "inline-block",
				backgroundColor: this.props.bgColor,
				borderRadius: "50%",
				width: 100,
				height: 100,
			};

			return (
				<div style={circleStyle}>
				</div>
			);
		}

	}

	ReactDOM.render(
		<div>
			{renderData}
		</div>,
		destination
	);
</script>
`

err code:
react.development.js:401 Warning: React.createElement: type is invalid – expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it’s defined in, or you might have mixed up default and named imports

I am learning react from your 9th edition book