[AngularJS] ngChange vs $scope.$watch

$scope.$watch

No matter the val change programmatically or munally, it will fire the binded function.

With AngularJS's $scope.$watch, you are able to monitor scope values for changes. This can be useful for validation of user input, as an example.

 

ngChange directive

ngChange only monitor on munally change NOT programmatically. 

The ngChange directive will allow you to monitor value changes on input elements in your AngularJS applications.

 

Read More:

https://egghead.io/lessons/angularjs-using-the-ngchange-directive-in-angular

 

复制代码
<!DOCTYPE html>
<html ng-app="app">
<head lang="en">
    <meta charset="UTF-8">
    <title>$watch</title>
    <script src="//cdnjs.cloudflare.com/ajax/libs/angular.js/1.2.20/angular.min.js"></script>
    <link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css"/>
    <style type="text/css">
        .panel {
            width: 70%;
            margin: 30px auto;
        }
    </style>
</head>
<body ng-controller="WatchCtrl">

<div class="panel panel-primary">
    <div class="panel-heading">
        <h3 class="panel-title">Create Account</h3>
    </div>
    <div class="panel-body">

        <form role="form">
            <div class="form-group">
                <label for="eml">Email address</label>
                <input id="eml"
                       type="email"
                       class="form-control"
                       placeholder="Email address"
                       ng-model="user.email">
            </div>
            <div class="form-group">
                <label for="pwd">Password</label>
                <input id="pwd"
                       type="password"
                       class="form-control"
                       placeholder="Password"
                       ng-change="onChange()"
                       ng-model="user.password">
            </div>
            <button type="submit" class="btn btn-default">Submit</button>
            <!-- This could call an "updatePassword" method on the controller
                  to modify this value. That method could also call $scope.$apply
                  so that the value would be updated with a digest cycle -->
            <button class="btn btn-danger"
                    ng-click="user.password = 'pwd'">Please Hack Me</button>
        </form>

    </div>
</div>

<div class="panel panel-danger" ng-show="showReqs">
    <div class="panel-heading">
        <h3 class="panel-title">Password Requirements</h3>
    </div>
    <div class="panel-body">
        <ul>
            <li ng-repeat="req in reqs">{{ req }}</li>
        </ul>
    </div>
</div>

<script src="app.js"></script>
</body>
</html>
复制代码
复制代码
function WatchCtrl ($scope) {

    function isLongEnough (pwd) {
        return pwd.length > 4;
    }

    function hasNumbers (pwd) {
        return /[0-9]/.test(pwd);
    }

    function checkPassword (value) {
        if (!value) return;

        $scope.reqs = [];

        if (!isLongEnough(value)) {
            $scope.reqs.push('Too short');
        }

        if (!hasNumbers(value)) {
            $scope.reqs.push('Must include numbers');
        }

        $scope.showReqs = $scope.reqs.length;
    }

    $scope.onChange = function () {
        checkPassword($scope.user.password);
    }
}

angular.module('app', [])
    .controller('WatchCtrl', WatchCtrl);
复制代码

 

posted @   Zhentiw  阅读(944)  评论(0)  编辑  收藏  举报
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