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Since the function is an event (blur) of the input, this inside the function will reference to the DOM Object input.

由于函数是输入的一个事件(模糊)，所以函数内部的这个函数将引用DOM对象输入。

To access jQuery functions like val() you need to transform it in a jQuery object. To do this, just enclose this in a $() accessor: $(this). This have the exact same result of $('input[name=id_num]'), but is faster since jQuery don't need to make the search on the object list.

要访问像val()这样的jQuery函数，需要在jQuery对象中进行转换。为此，只需将其包含在$()访问器:$(this)中。这与$('input[name=id_num]')的结果完全相同，但更快，因为jQuery不需要在对象列表上进行搜索。

The data line would then look like this:

数据线是这样的:

data: "idnum=" + $(this).val(),

Also take care with single quotes/double quotes. In your original code the result for data would be the string "idnum= ' + this.val + '". Single quotes enclosed by double quotes are included in the string and have no effect in splitting code area from string area.

也要注意单引号/双引号。在原始代码中，数据的结果将是字符串“idnum= ' + this。val +’”。用双引号括起来的单引号包含在字符串中，在从字符串区域分割代码区域时没有作用。