How to Use Reactjs List In a Website
Posted By : Vikas Pundir | 06-Nov-2019
ReactJS | Lists
The above code will log the below output to the console:
[3, 4, 5, 6]
Code illustrate this:
Here Rendering lists inside Components
In React code we had directly rendered the list to the DOM. But this, not a good practice to render lists in React. We already have talked about the uses of Components and had seen that everything in React is built as individual components. Consider the example of a Navigation Menu. It is obvious that on any website the items in a navigation menu are not hardcoded. Lists displayed in the browser after this item are fetched from the database . So from the component’s point of view, we can say that we will pass a list to a component using props and then use this component to render the list to the DOM. We can update the above code in which we have directly rendered the list to now a component that will accept an array as props and returns an unordered list.
But with this code, a warning message is logged to the console.
"Warning: Each child in an array have a unique "key" prop"
The above warning message says that each of the list items in our unordered list should have a unique key. A “key” is a special string attribute. When creating lists of elements in React you need to include Key. Now, we will assign a string key to each of our list items in the above code.
The updated code with keys:
We get the same output as that of the previous code but without any warning. To identify which items in the list are changed, updated or deleted we used Keys in React. We can say that keys are used to give an identity to the elements in the lists.