Understanding Ajax versions: Evolution from early days to modern times

Ajax is an important technology for creating dynamic web applications. As web applications continue to evolve, Ajax continues to evolve and improve. This article will explain in detail the development history of Ajax from the early days to the present, and give specific code examples.

1. Early Ajax

Early Ajax appeared around 2005, which allows Web pages to interact with the server without refreshing. At this stage, the technologies involved in using Ajax are still relatively basic. The most basic technologies include JavaScript, XML and XMLHttpRequest objects. The combination of these technologies allows web applications to communicate seamlessly between users and servers.

The following is a simple example of using Ajax to search without refreshing the page:

function search() {
  var searchValue = document.getElementById("searchInput").value;
  var xhr = new XMLHttpRequest();
  xhr.onreadystatechange = function() {
    if (xhr.readyState == 4 && xhr.status == 200) {
      document.getElementById("searchResult").innerHTML = xhr.responseText;
    }
  };
  xhr.open("GET", "/search?q=" + searchValue, true);
  xhr.send();
}

In this example, when the user enters a keyword in the search box and presses the search button, JavaScript will use the XMLHttpRequest object to send a GET request to the server. When the server returns search results, JavaScript displays the results on the page without refreshing the entire page.

2. The era of jQuery

With the continuous development of Ajax, jQuery has become the main choice for using Ajax. jQuery provides a simple and easy-to-use API, making using Ajax easier. Using jQuery, you can easily send various types of requests such as GET, POST, PUT, DELETE, etc.

The following is an example of using jQuery to search without refreshing the page:

function search() {
  var searchValue = $("#searchInput").val();
  $.get("/search?q=" + searchValue, function(data) {
    $("#searchResult").html(data);
  });
}

In this example, when the user enters keywords in the search box and presses the search button, JavaScript will Use jQuery's $.get() method to send a GET request to the server. When the server returns search results, jQuery displays the results on the page without refreshing the entire page.

3. Modern Ajax

Modern Ajax is no longer a simple combination of JavaScript, XML and XMLHttpRequest objects. Now, front-end developers have many frameworks and libraries to choose from, such as React, Vue.js, Angular, etc. These frameworks and libraries not only enable developers to use Ajax more efficiently, but also enable Web applications to perform better in terms of functionality and performance.

The following is an example of using Vue.js to implement search without refreshing the page:

<div id="app">
  <input type="text" v-model="searchValue">
  <button @click="search">Search</button>
  <div v-html="searchResult"></div>
</div>
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<script>
new Vue({
  el: "#app",
  data: {
    searchValue: "",
    searchResult: ""
  },
  methods: {
    search() {
      var self = this;
      fetch("/search?q=" + this.searchValue)
      .then(response => response.text())
      .then(data => {
        self.searchResult = data;
      });
    }
  }
});
</script>

In this example, when the user enters a keyword in the search box and presses the search button, Vue.js will execute the search() method. The fetch() function is used in the method to send a GET request to the server. When the server returns search results, Vue.js renders the results onto the page without refreshing the entire page.

Conclusion

The development history of Ajax is very long. From the early simple technology combination to the modern framework and library, its meaning and value are constantly expanded and deepened along the way. Although Ajax technology is already a very common choice in Web front-end development, developers still need to choose the most suitable technical solution based on specific application scenarios and needs during use.

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