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• Dynamic Key Generation In Map Function Reaction

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A “key” is a special string attribute you need to include when creating lists of elements in React. Keys are used in React to identify which items in the list are changed, updated or deleted. In other words we can say that keys are used to give an indentity to the elements in the lists. Feb 27, 2019 We will be using create-react-app to quickly set up our front end dev environment. Navigate to an empty directory and install create-react-app by running. Npm i create-react-app. Now lets generate our project using the following command. Npx create-react-app react-to-pdf. Once the project is generated, lets start the local server by running. The problem is that your map function is not bound to the outer this scope. So three ways: Using the second parameter of map to bind the context. Here on the person component, we're going to say key equals item.name. Save that, and everything is working fine. If we wanted to get a look at how we can further use this JSX generation from a data set, let's say if this.state.filter - we'll need to create that - but if we have a filter, we'll say items equal items.filter. The map method in JavaScript creates an array by calling a specific function on each element present in the parent array. It is a non-mutating method. Generally map method is used to iterate over an array and calling function on every element of array. Syntax: array.map(function(currentValue, index, arr), thisValue). Mar 28, 2018 Let us have a deep look at the model props as that is the heart of this dynamic form component. Key Unique ID. It is used as “key” prop the component and also this value is used for dynamically create the state value for the specific input in the DynamicForm component. Label The text to display on the label field of input.

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React keys are useful when working with dynamically created components or when your lists are altered by the users. Setting the key value will keep your components uniquely identified after the change.

Using Keys

Let's dynamically create Content elements with unique index (i). The map function will create three elements from our data array. Since the key value needs to be unique for every element, we will assign i as a key for each created element.

App.jsx

main.js

We will get the following result for the Key values of each element.

If we add or remove some elements in the future or change the order of the dynamically created elements, React will use the key values to keep track of each element.

A small library providing a utility method to list out React components and generate unique keys automatically

Installation

npm install react-keygen --save

Usage

Use reactKeyMap just like you would Array.map. However, no need to worry about finding and passing in a uniq key, reactKeyMap handles that for you! /serial-key-generator-for-adobe-photoshop-cs6-extended.html.

Each <ListItem /> component will have a uniq key created by hashing our data passed in.If you still wish to use your own keys you can still set it like you normally would, andreactKeyMap will default to the user provided key.

Behind the Curtain

The reactKeyMap utility function hashes the first argument you pass into the callback function, usually this will be an object. It passes this hash value in as the key prop by wrapping our normal map callback function in React.cloneElement.

It uses a 32 bit FNV-1 hash algorithm because FNV algorithms are simple, fast, and maintain a low collision rate. FNV hashes are also great at hashing almost identical strings, which is needed since most of the listed data in this context will be very similar.

FNV Hash Algorithm Advantages

• Fast
• Low collision rate
• High dispersion
• Simple implementation w/ little overhead

For more details see: http://www.isthe.com/chongo/tech/comp/fnv/

Tests

npm test

Release History

Dynamic Key Generation In Map Function Reaction

• 0.1.0 Initial release