我需要根据选择下拉菜单的哪个选项更新变量的值（我在示例中称为“tot”）。 如果我选择选项1或2 tot必须增加10，如果我选择选项3变量“tot”不得增加。 如果我选择选项1，然后我改变主意并选择选项3，则必须恢复Tot的值。
这是选择的html
<select name='hello' id='hello'> <option>Select an option...</option> <option id='one'>One</option> <option id='two'>Two</option> <option id='three'>Three</option> </select>这是我写的jquery脚本。 我想我不明白.change函数的功能，因为它不能像我预期的那样工作。
var extra = 0; var tot = 0; $(document).ready(function () { $('#hello').change(function(){ if($('#one').is(':selected')) { extra = 10; } else if($('#two').is(':selected')) { extra = 10; } else if($('#three').is(':selected')) { extra = 0; } tot = tot + extra; }); });I need to update the value of a variable (which I called "tot" in the example) according to what option of a dropdown menu is selected. If I select option 1 or 2 tot must be increased of 10, if I select option 3 variable "tot" must NOT be increased. If i select option 1, and then I change my mind and select option 3 the value of Tot must be restored.
Here's the html of the select
<select name='hello' id='hello'> <option>Select an option...</option> <option id='one'>One</option> <option id='two'>Two</option> <option id='three'>Three</option> </select>And here's the jquery script I wrote. I guess I didn't understand the functioning of .change function, because it doesn't work as I expected.
var extra = 0; var tot = 0; $(document).ready(function () { $('#hello').change(function(){ if($('#one').is(':selected')) { extra = 10; } else if($('#two').is(':selected')) { extra = 10; } else if($('#three').is(':selected')) { extra = 0; } tot = tot + extra; }); });最满意答案
或者（如果我已经理解了你正确的话）....
var tot = 120; //some number picked at random var helloed = false; // flag for whether incremented $(document).ready(function(){ $("#hello").change(function(){ var sel = $(this).find(":selected").attr("id") if (sel == "one" || sel =="two" ) { if (!helloed) { tot += 10; helloed = true; } } else { // 'three' selected if (helloed) { tot -= 10; helloed = false; } } alert ("Tot is now " + tot); }); });如果有更多选项，我会选择开关而不是IF，但这样做可以用于此示例
Or (if I've understood what you're after correctly)....
var tot = 120; //some number picked at random var helloed = false; // flag for whether incremented $(document).ready(function(){ $("#hello").change(function(){ var sel = $(this).find(":selected").attr("id") if (sel == "one" || sel =="two" ) { if (!helloed) { tot += 10; helloed = true; } } else { // 'three' selected if (helloed) { tot -= 10; helloed = false; } } alert ("Tot is now " + tot); }); });If there were more options I'd go for a switch rather than an IF but that will do for this example
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