Functions can have default arguments, as shown for the value argument of the compute function.

函数可以有默认参数，如compute函数的值参数所示。

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You can use the line of code shown in Listing 6 to specify a default value for an argument that is absent.

您能够使用清单6中所示代码行来为缺失的参数指定默认值。

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This handler prevents the default event (submitting the form) from being fired, sets the value of the extra ajax argument to 1, and makes an ajax Request using the original form for the URL and data.

这个处理程序阻止默认事件(提交表单)触发，将额外的ajax参数的值设置为1，使用原始表单发出一个ajax请求以获取URL和数据。

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