[英]How to determine if a Javascript class has been declared?
I have some javascript that is being referenced via html that is loaded via AJAX (ie: AJAX retrieves HTML, HTML has a <script>
tag in it that references this javascript) 我有一些通过AJAX加载的html被引用的javascript(即:AJAX检索HTML,HTML中有一个
<script>
标记引用了此javascript)
This javascript contains class declarations, ex: 此javascript包含类声明,例如:
class CalculatorClass{
...
}
If this script gets loaded twice, I get an error: redeclaration of let CalculatorClass
. 如果此脚本被加载两次,则会出现错误:
redeclaration of let CalculatorClass
。 Since it's not a variable, I can't test if it's undefined
first - and even then it would restrict the scope. 由于它不是一个变量,因此我无法先测试它是否
undefined
-即使那样也会限制范围。 How do I only declare the class if it isn't already? 如果尚未声明该类,我该如何声明呢?
您可以使用if (typeof MyClass === 'function')
检查是否已声明一个类。
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