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angularjs study notes two-way data binding_AngularJS

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May 16, 2016 pm 03:38 PM

angularjsTwo-way data binding

This time we will explain angular’s two-way data binding in detail.

1. Simple example

We have already shown this example in the first section. To see it, go 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 binding of data.

2. 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 a value expression, but if you keep refreshing the page, you You will find such a problem, that is, the string "{{greeting.text}} {{text}}" will sometimes appear on the page for a moment. So how should we solve it?

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

For example, we can put

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

Change 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.

3. Typical scenarios of two-way binding - form

First look at the content of 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>
 <div class="panel panel-primary">
  <div class="panel-heading">
   <div class="panel-title">双向数据绑定</div>
  </div>
  <div class="panel-body">
   <div class="row">
    <div class="col-md-12">
     <form class="form-horizontal" role="form" ng-controller="UserInfoCtrl">
      <div class="form-group">
       <label class="col-md-2 control-label">
        邮箱：
       </label>
       <div class="col-md-10">
        <input type="email" class="form-control" placeholder="推荐使用126邮箱" ng-model="userInfo.email">
       </div>
      </div>
      <div class="form-group">
       <label class="col-md-2 control-label">
        密码：
       </label>
       <div 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">
       </div>
      </div>
      <div class="form-group">
       <div class="col-md-offset-2 col-md-10">
        <div class="checkbox">
         <label>
          <input type="checkbox" ng-model="userInfo.autoLogin">自动登录
         </label>
        </div>
       </div>
      </div>
      <div class="form-group">
       <div 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>
       </div>
      </div>
     </form>
    </div>
   </div>
  </div>
 </div>
</body>

</html>

Look at the content of Form.js again:

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

The screenshot of the effect is as follows:

The functions implemented in the above picture are:

1. Click "Get" to 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 the unchecked status of the check box;

3. Click "Reset": you can restore the data to the original data.

Since 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! Go ahead!

4. Dynamically switch label styles

Look at the content of color.html first:

<!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>
  <div ng-controller="CSSCtrl">
    <p class="text-{{color}}">测试CSS样式</p>
    <button class="btn btn-default" ng-click="setGreen()">绿色</button>
  </div>
</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 the p tag. When “green” is clicked, the setGreen function is executed and the value of “color” is changed to “green”, so the class name is changed. , which also changes 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('MyCSSModule', []);
myCSSModule.controller('CSSCtrl', ['$scope',
  function($scope) {
    $scope.color = "red";
    $scope.setGreen = function() {
      $scope.color = "green";
    }
  }
])

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

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