如何判断属性是否存在且是否为假 [英] how to tell if a property exists and is false
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问题描述
我很难确定传入jquery模板的数据是否存在,并且在没有出错的情况下为false。这就是我用来测试的内容
< html>
< head>
< title> jQuery模板{{if}}逻辑< / title>
< / head>
< body>
< p id =results>< / p>
< p>如何测试Value是否存在且为false?< / p>
< script id =testTemplatetype =text / html>
测试$ {测试}:
{{如果值}}
值存在且为真
{{else}}
价值不存在或为假
{{/ if}}
< br />
< / script>
< script type =text / javascriptsrc =http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js>< ; /脚本>
< script type =text / javascriptsrc =jquery.tmpl.min.js>< / script>
< script type =text / javascript>
$(document).ready(function(){
$(#testTemplate)。tmpl({Test:1})。appendTo(#results);
$( #testTemplate)。tmpl({Test:2,Value:true})。appendTo(#results);
$(#testTemplate)。tmpl({Test:3,Value:false} ).appendTo(#results);
});
< / script>
< / body>< / html>
有谁知道怎么做?
=== false $ c c>检查,如下所示:
{{if Value}}
值存在且为真
{{else typeof(Value)!=undefined&&值=== false}}
值存在且为false
{{else}}
值不存在或未明确错误
{{/ if}}
你可以在这里测试一下。 typeof
检查是因为您将获得未定义值
错误仅 值=== false
。您还可以添加其他检查,例如 {{else typeof(Value)==undefined}}
如果未指定值,则为true。
I am having a hard time determining if data passed into the jquery template exists and is false without getting errors. This is what I am using to test
<html>
<head>
<title>jQuery Templates {{if}} logic</title>
</head>
<body>
<p id="results"></p>
<p>How do you test if the Value exists and is false?</p>
<script id="testTemplate" type="text/html">
Test ${Test}:
{{if Value}}
Value exists and is true
{{else}}
Value doesn't exist or is false
{{/if}}
<br/>
</script>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script type="text/javascript" src="jquery.tmpl.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$("#testTemplate").tmpl({Test:1}).appendTo("#results");
$("#testTemplate").tmpl({Test:2, Value:true}).appendTo("#results");
$("#testTemplate").tmpl({Test:3, Value:false}).appendTo("#results");
});
</script>
</body></html>
Does anyone know how to do it?
解决方案
You can use another else
statement in there using a === false
check, like this:
{{if Value}}
Value exists and is true
{{else typeof(Value) != "undefined" && Value === false}}
Value exists and is false
{{else}}
Value doesn't exist or isn't explicitly false
{{/if}}
You can test it out here. The typeof
check is because you'll get a Value is not defined
error with only Value === false
. You would add other checks as well, for example {{else typeof(Value) == "undefined"}}
would be true if the value wasn't specified.
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