<!DOCTYPE html>
<html lang="zh">
    <head>
        <meta charset="utf-8" />
        <title>FireBase Example</title>
        <script src="https://www.gstatic.com/firebasejs/4.9.1/firebase.js"></script>
        <script>
          // Initialize Firebase
          var config = {
            apiKey: "AIzaSyAOSPYpgn7T_bKa6VbCaSeQlsw-3p3zqDs",
            authDomain: "yiibai-firebase.firebaseapp.com",
            databaseURL: "https://yiibai-firebase.firebaseio.com/",
            projectId: "yiibai-firebase",
            storageBucket: "yiibai-firebase.appspot.com",
            messagingSenderId: "334522625008"
          };
          firebase.initializeApp(config);
         var firstPlayerRef = firebase.database().ref("players/").limitToFirst(2);
          var lastPlayerRef = firebase.database().ref('players/').limitToLast(2);
            //console.log("====== limitToFirst(2) ========");
            firstPlayerRef.on("value", function(data) {
               console.log(data.val());
            }, function (error) {
               console.log("Error: " + error.code);
            });
            console.log("====== limitToLast(2) ========");
            lastPlayerRef.on("value", function(data) {
               console.log(data.val());
            }, function (error) {
               console.log("Error: " + error.code);
            });
        </script>
    </head>
<body>

控制臺(tái)會(huì)記錄第一個(gè)查詢得到前兩個(gè)運(yùn)動(dòng)員數(shù)據(jù)，第二個(gè)查詢得到最后兩個(gè)運(yùn)動(dòng)員數(shù)據(jù)。結(jié)果如下所示 -

其他過濾器

我們也可以使用其他Firebase過濾方法。例如:startAt()，endAt()和equalTo()可以與排序方法結(jié)合使用。在下面的例子中，我們將把它和orderByChild()方法結(jié)合起來。

示例

讓我們來看看下面的例子。參考以下代碼 -

<!DOCTYPE html>
<html lang="zh">
    <head>
        <meta charset="utf-8" />
        <title>FireBase Example</title>
        <script src="https://www.gstatic.com/firebasejs/4.9.1/firebase.js"></script>
        <script>
          // Initialize Firebase
          var config = {
            apiKey: "AIzaSyAOSPYpgn7T_bKa6VbCaSeQlsw-3p3zqDs",
            authDomain: "yiibai-firebase.firebaseapp.com",
            databaseURL: "https://yiibai-firebase.firebaseio.com/",
            projectId: "yiibai-firebase",
            storageBucket: "yiibai-firebase.appspot.com",
            messagingSenderId: "334522625008"
          };
          firebase.initializeApp(config);
         var firstPlayerRef = firebase.database().ref("players/").limitToFirst(2);
            var playersRef = firebase.database().ref("players/");

            playersRef.orderByChild("name").startAt("Kobe").on("child_added", function(data) {
               console.log("Start at filter: " + data.val().name);
            });

            playersRef.orderByChild("name").endAt("Maxsu").on("child_added", function(data) {
               console.log("End at filter: " + data.val().name);
            });

            playersRef.orderByChild("name").equalTo("Kobe").on("child_added", function(data) {
               console.log("Equal to filter: " + data.val().name);
            });

            playersRef.orderByChild("age").startAt(20).on("child_added", function(data) {
               console.log("Age filter: " + data.val().name);
            });
        </script>
    </head>
<body>

結(jié)果如下所示 -

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Firebase過濾數(shù)據(jù)

限制第一個(gè)和最后一個(gè)

其他過濾器