jQuery：即使在处理数字时，我也必须使用parseInt（），为什么？

Question

i have the following script

<select id="select1">
      <option value="1">1day</option>
      <option value="2">2day</option>
      <option value="3">3day</option>
    </select>

    <select id="select2">
      <option value="1">1day</option>
      <option value="2">2day</option>
      <option value="3">3day</option>
    </select>

and jquery

$("#select2").change(function() {
            var max_value = parseInt($("#select2 :selected").val());
            var min_value = parseInt($("#select1 :selected").val());
            if(max_value < min_value)
            {
              $("#select1").val($(this).val());
            }
        });

and now, what i can't understand anyway - if values of option elements are integer numbers, why i have to use parseInt()? in some cases it doesn't work without parseInt().

Thanks

Answer 1

Form field values are always stored as strings. Whether or not they look like integers is irrelevant; they're strings. You need to convert them to integers before treating them as such :)

Answer 2

http://www.uvsc.edu/disted/decourses/mct/2760/IN/krutscjo/lessons/06/ff_05.html

Javascript treats most everything as a string unless you explicitly tell it that it is a number. One notable example of this is getting values from form elements. Depending on the browser and user input you may get some unexpected results.

Answer 3

值永远不是整数，事实上，您将数字放在那里而不是谁知道，这只是您的选择。

Answer 4

jQuery's val() function always returns a string. In many cases you can mix numbers and strings (in arithmic for example), when comparing two string variables, javascript will perform a string comparison, not a numeric comparison (which is to be expected)