This tutorial will teach you how to use Axios to get data, then how to manipulate it and finally display it on your page through filtering. Along the way you'll learn how to use mapping, filters, and include methods. Most importantly, you will create a simple loader to handle the loading status of data obtained from the API endpoint.

1. Setup Project

Let’s set up a React project using the create-react-app command in the terminal:

npx create-react-app project-name

Then, open the project directory through a terminal window and enter npm install axios to install Axios locally for the project.

2.Select target API

We will use the Random User Generator API to get random user information to use in our application.

Let's add the Axios module to our application by importing it into our App.js file.

import axios from 'axios'

The Random User Generator API provides a range of options for creating various types of data. You can check out the documentation for more information, but for this tutorial we'll keep it simple.

We want to get ten different users, we just need the first name, last name, and unique ID, which is what React needs when creating the list of elements. Also, to make the call more specific, let's take the nationality option as an example.

Here is the API URL we will call:

https://randomuser.me/api/?results=10&inc=name,registered&nat=fr

Please note that I did not use the id option provided in the API as it sometimes returns null for some users. Therefore, to ensure that each user has a unique value, I included the registered option in the API.

You can copy and paste this into your browser and you will see the data returned in JSON format.

Now, the next step is to make the API call through Axios.

3. Create application state

First, let's create a state using the useState hook in React so that we can store the fetched data.

In our App component, import the useState hook from React and create the state as shown below.

import React, { useState } from "react";
import axios from "axios";

const App = () => {
  const [users, setUsers] = useState([]);
  const [store, setStore] = useState([]);

  return (
    <div>
     
    </div>
  );
};

export default App;

Here you can see the users and store status. One will be used for filtering purposes and will not be edited, the other will hold the filtered results that will be displayed in the DOM.

4.Use axios to obtain data

The next thing we need to do is create a getUsers function to handle the acquisition of data. In this function, we use axios to get the data from the API using the get method.

Now, in order to display the data we fetched when the page loads, we will import a React hook named useEffect and call the getUsers function in it.

useEffect The hook basically manages side effects in functional components and is similar to the componentDidMount() lifecycle hook used in React class-based components. This hook accepts an empty array as second argument for side effect cleanup.

Update the code in the App component as shown below so that we can inspect the response data in the console.

import React, { useState, useEffect } from "react";

const App = () => {
  const [users, setUsers] = useState([]);
  const [store, setStore] = useState([]);
  
  const getUsers = () => {
    axios.get("https://randomuser.me/api/?results=10&inc=name,registered&nat=fr")
      .then(response => console.log(response))
  };
  
  useEffect(() => {
    getUsers();
  }, []);

  return (
    <div>
     
    </div>
  );
};

export default App;

When you check the console you will see an object output. If you open this object, there is another object inside, named data, and inside data, there is an array named results.

If we want to return a specific value from the result, we can update the axios.get call as follows:

    axios.get("https://randomuser.me/api/?results=10&inc=name,registered&nat=fr")
      .then(response => console.log(response.data.results[0].name.first))

Here we record the name of the first value in the result array.

5.Processing result data

Now let’s use JavaScript’s built-in map method to iterate over each element in the array and create a new array of JavaScript objects with a new structure.

Update your getUsers function with the following code:

  const getUsers = () => {
    axios
      .get("https://randomuser.me/api/?results=10&inc=name,registered&nat=fr")
      .then((response) => {
        const newData = response.data.results.map((result) => ({
          name: `${result.name.first} ${result.name.last}`,
          id: result.registered
        }));
        setUsers(newData);
        setStore(newData);
      })
      .catch((error) => {
        console.log(error);
      });
  };

In the above code, we created a variable named newData. It stores the results of viewing the response.data.results array using the map method. In the map callback, we reference each element of the array as a result (note the singular/plural difference). Additionally, by using the key-value pairs for each object in the array, we create another object using the name and id key-value pairs.

一般情況下，在瀏覽器中查看API調(diào)用結(jié)果，會看到里面有first 和last 鍵值對name 對象，但沒有全名的鍵值對。因此，從上面的代碼中，我們能夠組合 first 和 last 名稱，在新的 JavaScript 對象中創(chuàng)建全名。請注意，JSON 和 JavaScript 對象是不同的東西，盡管它們的工作方式基本相同。

然后我們將新的中間數(shù)據(jù)設(shè)置為 setUsers 和 setStore 狀態(tài)。

6. 通過過濾填充數(shù)據(jù)存儲

過濾的想法非常簡單。我們有我們的 store 狀態(tài)，它始終保持原始數(shù)據(jù)不變。然后，通過在該狀態(tài)上使用 filter 函數(shù)，我們只獲取匹配的元素，然后將它們分配給 users 狀態(tài)。

const filteredData = store.filter((item) => (
    item.name.toLowerCase().includes(event.target.value.toLowerCase()))

filter 方法需要一個函數(shù)作為參數(shù)，該函數(shù)針對數(shù)組中的每個元素運(yùn)行。這里我們將數(shù)組中的每個元素稱為 item。然后，我們獲取每個 item 的 name 鍵并將其轉(zhuǎn)換為小寫，以使我們的過濾功能不區(qū)分大小寫。

獲得 item 的 name 鍵后，我們檢查該鍵是否包含我們輸入的搜索字符串。 includes 是另一個內(nèi)置 JavaScript 方法。我們將在輸入字段中鍵入的搜索字符串作為參數(shù)傳遞給 includes，如果該字符串包含在調(diào)用它的變量中，則它會返回。同樣，我們將輸入字符串轉(zhuǎn)換為小寫，這樣無論您輸入大寫還是小寫輸入都無關(guān)緊要。

最后，filter方法返回匹配的元素。因此，我們只需將這些元素存儲在 setUsers 狀態(tài)中即可。

使用我們創(chuàng)建的函數(shù)的最終版本更新 App 組件。

 const filterNames = (event) => {
    const filteredData = store.filter((item) =>
      item.name.toLowerCase().includes(event.target.value.toLowerCase())
    );
    setUsers(filteredData);
  };

7. 創(chuàng)建組件

盡管對于這個小示例，我們可以將所有內(nèi)容放入 App 組件中，但讓我們利用 React 并制作一些小型功能組件。

讓我們向應(yīng)用程序添加幾個組件。首先，我們從單獨(dú)的 JavaScript 文件導(dǎo)入組件（我們將很快定義這些文件）：

import Lists from "./components/Lists";
import SearchBar from "./components/SearchBar";

接下來，我們更新應(yīng)用程序組件的 return 語句以使用這些組件：

  return (
    <div className="Card">
        <div className="header">NAME LIST</div>
        <SearchBar searchFunction={filterNames} />
        <Lists usernames={users} />
    </div>
  );

目前，我們將只關(guān)注功能。稍后我將提供我創(chuàng)建的 CSS 文件。

請注意，我們有 searchFunction 屬性用于 SearchBar 組件，以及 usernames 屬性用于 Lists 組件.

另請注意，我們使用 users 狀態(tài)而不是 store 狀態(tài)來顯示數(shù)據(jù)，因?yàn)?users 狀態(tài)包含已過濾的數(shù)據(jù)結(jié)果。

SearchBar 組件

這個組件非常簡單。它僅將 filterNames 函數(shù)作為 prop，并在輸入字段更改時調(diào)用該函數(shù)。將以下代碼放入 components/SearchBar.js 中：

import React from 'react';

const SearchBar = ({ searchFunction}) => {
  return (
    <div>
        <input className="searchBar" type='search' onChange={searchFunction} />
    </div>
  )
};

export default SearchBar;

列表組件

該組件將簡單地列出用戶的姓名。這位于 components/List.js 中：

import React from 'react';

const Lists = ({ usernames }) => {
  return (
      <div>
          <ul>
              {usernames.map(username => (
                  <li key={username.id}>{username.name}</li>
              ))}
          </ul>
      </div>
  )
};

export default Lists;

在這里，我們再次使用 map 方法來獲取數(shù)組中的每個項(xiàng)目，并從中創(chuàng)建一個 <li> 項(xiàng)目。請注意，當(dāng)您使用 map 創(chuàng)建項(xiàng)目列表時，您需要使用 key 以便 React 跟蹤每個列表項(xiàng)目。

8.跟蹤加載狀態(tài)

讓我們使用 useState 掛鉤創(chuàng)建一個加載狀態(tài)，以顯示何時尚未獲取數(shù)據(jù)。

  const [loading, setLoading] = useState(false);

接下來，我們將更新數(shù)據(jù)獲取方法中的加載狀態(tài)。

  const getUsers = () => {
    axios.get("https://randomuser.me/api/?results=10&inc=name,registered&nat=fr")
      .then((response) => {
        const newData = response.data.results.map((result) => ({
          name: `${result.name.first} ${result.name.first}`,
          id: result.registered,
        }));
        setLoading(true);
        setUsers(newData);
        setStore(newData);
      })
      .catch((error) => {
        console.log(error);
      });
  };

在這里，我們創(chuàng)建了一個 loading 狀態(tài)并將其初始設(shè)置為 false。然后我們在使用 setLoading 狀態(tài)獲取數(shù)據(jù)時將此狀態(tài)設(shè)置為 true。

最后，我們將更新 return 語句以呈現(xiàn)加載狀態(tài)。

  return (
    <>
      {loading ? (
        <div className="Card">
          <div className="header">NAME LIST</div>
          <SearchBar searchFunction={filterNames} />
          <Lists users={users} />
        </div>
      ) : (
        <div className="loader"></div>
      )}
    </>
  );

使用 JavaScript 三元運(yùn)算符，我們在加載狀態(tài)為 false 時有條件地渲染 SearchBar 和 Lists 組件，然后在加載狀態(tài)為 true 時渲染加載程序。另外，我們創(chuàng)建了一個簡單的加載器來在界面中顯示加載狀態(tài)。

9. 添加一些 CSS 進(jìn)行樣式設(shè)置

您可以在下面找到特定于此示例的 CSS 文件。

body,
html {
  -webkit-font-smoothing: antialiased;
  margin: 0;
  padding: 0;
  font-family: "Raleway", sans-serif;
  -webkit-text-size-adjust: 100%;
}

body {
  display: flex;
  justify-content: center;
  font-size: 1rem/16;
  margin-top: 50px;
}

li,
ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

ul {
  margin-top: 10px;
}

li {
  font-size: 0.8rem;
  margin-bottom: 8px;
  text-align: center;
  color: #959595;
}

li:last-of-type {
  margin-bottom: 50px;
}

.Card {
  font-size: 1.5rem;
  font-weight: bold;
  display: flex;
  flex-direction: column;
  align-items: center;
  width: 200px;
  border-radius: 10px;
  background-color: white;
  box-shadow: 0 5px 3px 0 #ebebeb;
}

.header {
  position: relative;
  font-size: 20px;
  margin: 12px 0;
  color: #575757;
}

.header::after {
  content: "";
  position: absolute;
  left: -50%;
  bottom: -10px;
  width: 200%;
  height: 1px;
  background-color: #f1f1f1;
}

.searchBar {
  text-align: center;
  margin: 5px 0;
  border: 1px solid #c4c4c4;
  height: 20px;
  color: #575757;
  border-radius: 3px;
}

.searchBar:focus {
  outline-width: 0;
}

.searchBar::placeholder {
  color: #dadada;
}

.loader {
  border: 15px solid #ccc;
  border-top: 15px solid #add8e6; 
  border-bottom: 15px solid #add8e6;
  border-radius: 50%;
  width: 80px;
  height: 80px;
  animation: rotate 2s linear infinite;
}

@keyframes rotate {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

結(jié)論

在本教程中，我們使用隨機(jī)用戶生成器 API 作為隨機(jī)數(shù)據(jù)源。然后，我們從 API 端點(diǎn)獲取數(shù)據(jù)，并使用 map 方法在新的 JavaScript 對象中重構(gòu)結(jié)果。

接下來是使用 filter 和 includes 方法創(chuàng)建過濾函數(shù)。最后，我們創(chuàng)建了兩個不同的組件，并在尚未獲取數(shù)據(jù)時有條件地以加載狀態(tài)渲染我們的組件。

在過去的幾年里，React 越來越受歡迎。事實(shí)上，我們在 Envato Market 中有許多項(xiàng)目可供購買、審查、實(shí)施等。如果您正在尋找有關(guān) React 的其他資源，請隨時查看它們。

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