How i should set javascript global variable to get its value properly

Question

I have two html elements on my page. One is dropdown and other is text field(which is working as autocomplete).

     <select id="match_engine_brand" name="match_engine[brand]" class="hidden-field"><option value="">Select Brand</option><option value="3">addidas</option>
        <option value="5">cat</option>
        <option value="2">nike</option>
        <option value="4">panther</option>
        <option value="6">tower</option></select>

while text field is

     <input class="string required ui-autocomplete-input" id="match_engine_shoe_model" name="match_engine[shoe_model]" placeholder="select model of shoe using autocomplete" required="required" size="50" type="text" autocomplete="off">

My cofeescript code is below

     $(document).ready ->

       $("#match_engine_brand").change ->
           window.flag_value =  $(this).val()
           alert(window.flag_value) #value display in alert

       $('#match_engine_shoe_model').autocomplete
         source: "/user/match_shoes/shoes?id="+window.flag_value
         select: (event, ui) -> $("#match_engine_shoe_model").val(ui.item.id)

In autocomplete function

window.flag_value       #give me undefined value    
$('#match_engine_brand :selected').val()   #give me undefined value

How i can get dropdown value in autocomplete function.

Thanks for help

Billy Chan · Accepted Answer · 2013-06-14 18:10:12Z

2

You need to have an initiated value of window.flag_value. Otherwise if you don't change #match_engine_branch, this var has no value. That's the reason of undefined value.

The way to solve it is to define this var before

$(document).ready ->
  window.flag_value = "something"
  ...

However I think it's unnecessary to use global var. Check it in function should work.

$('#match_engine_shoe_model').autocomplete ->
  dropdown_value = $("#match_engine_brand").val() ? "something"

edited Jun 14, 2013 at 18:10

answered Jun 14, 2013 at 13:54

Billy Chan

24.8k4 gold badges55 silver badges69 bronze badges

dropdown_value = $("#match_engine_brand").val() || "something". This line in autocomplete give me syntax error. If i write this properly then my problem will be solved. please help
– Muhammad Kashif Ali
Commented Jun 14, 2013 at 17:47
help me please i have describe my problem above
– Muhammad Kashif Ali
Commented Jun 14, 2013 at 17:48
@Kashiftufail, I get used to Ruby's pipes equal and forget Coffee's special syntax :) Question mark is the right way to go. Sorry about that. Fixed.
– Billy Chan
Commented Jun 14, 2013 at 18:11
a = b || c is perfectly valid syntax...
– Alex Wayne
Commented Jun 14, 2013 at 18:13
1

@AlexWayne, thanks for mentioning that. I tried both of them in my console, d = a || "something" raised "Reference error: a is not defined", while d = a ? "something" actually returned "something". See coffeescript.org/#operators - The existential operators for details. I think ? is more suitable for this case as val() could be either undefined or null.
– Billy Chan
Commented Jun 14, 2013 at 18:21

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