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Angularjs study notes two-way data binding

高洛峰Original: 2016-12-24 10:07:261395browse

This time we will explain in detail the two-way data binding of angular.

1. Simple example

We have already shown this example in the first section. To see it, move here

The effect achieved here is that when you enter content in the input box, the corresponding content will be changed accordingly. . This achieves two-way data binding.

2. The use of value expressions and ng-bind

Let’s look at another example, click here. In the first example that appears in the article, {{greeting.text}} and {{text}} are one Value expression, but if you keep refreshing the page, you will find such a problem, that is, the string "{{greeting.text}} {{text}}" will sometimes appear on the page for a moment, then we should How to solve it?

The ng-bind command is used here: used to bind data expressions.

For example, we can change

<p>{{greeting.text}} {{text}}</p>

to:

"<p><span ng-bind="greeting.text"></span><span ng-bind="text"></span></p>";

After this correction, the unwanted string will not appear when the page is refreshed.

　But using commands is always less efficient than using expressions directly, so we have summarized a common rule: Generally speaking, index uses ng-bind, and subsequent templates use the form of '{{}}'.

3. Typical scenario of two-way binding - form

First look at the content of a form.html:

<!doctype html>
<html ng-app="UserInfoModule">
 
<head>
 <meta charset="utf-8">
 <link rel="stylesheet" href="css/bootstrap-3.0.0/css/bootstrap.css">
 <script src="js/angular-1.3.0.js"></script>
 <script src="Form.js"></script>
</head>
 
<body>
 <p class="panel panel-primary">
  <p class="panel-heading">
   <p class="panel-title">双向数据绑定</p>
  </p>
  <p class="panel-body">
   <p class="row">
    <p class="col-md-12">
     <form class="form-horizontal" role="form" ng-controller="UserInfoCtrl">
      <p class="form-group">
       <label class="col-md-2 control-label">
        邮箱：
       </label>
       <p class="col-md-10">
        <input type="email" class="form-control" placeholder="推荐使用126邮箱" ng-model="userInfo.email">
       </p>
      </p>
      <p class="form-group">
       <label class="col-md-2 control-label">
        密码：
       </label>
       <p class="col-md-10">
        <input type="password" class="form-control" placeholder="只能是数字、字母、下划线" ng-model="userInfo.password">
       </p>
      </p>
      <p class="form-group">
       <p class="col-md-offset-2 col-md-10">
        <p class="checkbox">
         <label>
          <input type="checkbox" ng-model="userInfo.autoLogin">自动登录
         </label>
        </p>
       </p>
      </p>
      <p class="form-group">
       <p class="col-md-offset-2 col-md-10">
        <button class="btn btn-default" ng-click="getFormData()">获取Form表单的值</button>
        <button class="btn btn-default" ng-click="setFormData()">设置Form表单的值</button>
        <button class="btn btn-default" ng-click="resetForm()">重置表单</button>
       </p>
      </p>
     </form>
    </p>
   </p>
  </p>
 </p>
</body>
 
</html>

Then look at the content of Form.js:

var userInfoModule = angular.module(&#39;UserInfoModule&#39;, []);
userInfoModule.controller(&#39;UserInfoCtrl&#39;, [&#39;$scope&#39;,
 function($scope) {
  $scope.userInfo = {
   email: "253445528@qq.com",
   password: "253445528",
   autoLogin: true
  };
  $scope.getFormData = function() {
   console.log($scope.userInfo);
  };
  $scope.setFormData = function() {
   $scope.userInfo = {
    email: &#39;testtest@126.com&#39;,
    password: &#39;testtest&#39;,
    autoLogin: false
   }
  };
  $scope.resetForm = function() {
   $scope.userInfo = {
    email: "253445528@qq.com",
    password: "253445528",
    autoLogin: true
   };
  }
 }
])

The function implemented in the above picture is:

　　 1. Click "Get", you can output three data on the console, email, password and selected status (true, false)

　　 2. Click "Settings": you can change the values of the two input boxes and cancel the check box Selected state;

　　3. Click "Reset": the data can be restored to the original data.

　Because the ng-model in the input box and the value in the controller implement two-way binding, changing the value of the input box or changing the value in the controller will change the values of both parties accordingly. Just a few lines of code can achieve such a powerful function. Don’t you think it’s amazing? It’s indeed amazing, but what’s even more amazing is yet to come! continue!

4. Dynamically switch label styles

First look at the content of color.html:

<!doctype html>
<html ng-app="MyCSSModule">
 
<head>
  <meta charset="utf-8">
  <link rel="stylesheet" href="CSS1.css">
</head>
<style type="text/css">
  .text-red {
    background-color: #ff0000;
  }
  .text-green {
    background-color: #00ff00;
  }
</style>
 
<body>
  <p ng-controller="CSSCtrl">
    <p class="text-{{color}}">测试CSS样式</p>
    <button class="btn btn-default" ng-click="setGreen()">绿色</button>
  </p>
</body>
<script src="js/angular-1.3.0.js"></script>
<script src="color.js"></script>
 
</html>

Let’s look at line 19: There is a "color" variable in this p tag. When "green" is clicked ”, execute the setGreen function and change the value of “color” to “green”, so the class name is changed, thereby also changing the background color. Using this method, we don't have to directly manipulate the elements, but just add a variable. The code is concise and intuitive.

　 Let’s take a look at the content of color.js again:

var myCSSModule = angular.module(&#39;MyCSSModule&#39;, []);
myCSSModule.controller(&#39;CSSCtrl&#39;, [&#39;$scope&#39;,
  function($scope) {
    $scope.color = "red";
    $scope.setGreen = function() {
      $scope.color = "green";
    }
  }
])

　 The default value of the attribute "color" is "red", so it displays red, and when clicked, the function is executed and turns green.

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