Comparing a Variable to an Array Element Not Working [Javascript]

Question

Being new to javascript I have come across an odd issue. I have an array of elements and a variable, I want to compare that variable to all array elements and do something if they match .

Here is the snippet of code:

for (var i=0; i<country_arr.length; i++) {

    option_str.options[option_str.length] = new Option(country_arr[i],country_arr[i]);

    if(selected_country == country_arr[i]){
        option_str.options[i].selected = true;
    }
}

The array itself is an array of strings:

var country_arr = new Array("Republic of Ireland", "Northern Ireland");

For whatever reason this does not enter the if statement but oddly enough when i replace:

if(selected_country == country_arr[i])

with:

if(selected_country == "Republic of Ireland")

...it does and works perfectly.

Am I comparing the two elements incorrectly? Any help would be greatly appreciated.

UPDATE - FULL .js FILE:

Full External .js File:

//Create a new array, to contain the list of countries available.
var country_arr = new Array("Republic of Ireland", "Northern Ireland");
//Create a new array to hold a list of counties depending on country selection.
var s_a = new Array();
s_a[0]="";
s_a[1]="Carlow|Cavan|Clare|Cork|Donegal|Dublin|Galway|Kerry|Kildare|Kilkenny|Laois|Leitrim|Limerick|Longford|Louth|Mayo|Meath|Monaghan|Offaly|Roscommon|Sligo|Tipperary|Waterford|Westmeath|Wexford|Wicklow";
s_a[2]="Antrim|Armagh|Down|Dungannon|Derry|Tyrone";

function print_country(country_id, selected_country){
    //Given the id of the <select> tag as function argument, it inserts <option> tags
    var option_str = document.getElementById(country_id);
    option_str.length=0;
    option_str.options[0] = new Option('Select Country','');
    option_str.selectedIndex = 0;
    for (var i=0; i<country_arr.length; i++) {
        option_str.options[option_str.length] = new     Option(country_arr[i],country_arr[i]);

        if(selected_country == country_arr[i]){
            option_str.options[i].selected = true;
            print_county('county',i);
        }
    }
}

function print_county(state_id, state_index){
    var option_str = document.getElementById(state_id);
    option_str.length=0;    // Fixed by Julian Woods
    option_str.options[0] = new Option('Select County','');
    option_str.selectedIndex = 0;
    var state_arr = s_a[state_index].split("|");

    for (var i=0; i<state_arr.length; i++) {
        option_str.options[option_str.length] = new Option(state_arr[i],state_arr[i]);
    }
}

The function is called and the variable selected_country is set via a php file using:

<script language="javascript">
    var selected = <?php echo json_encode($g_country); ?>;
    print_country("country", selected);
</script>

Have you stepped through the loop with a debugger? Could you provide a a complete minimally sufficient example? — Matt Ball
– Matt Ball, Commented Mar 5, 2014 at 1:54
if you are not practising your javascript then use Lo-Dash lib lodash.com — wayne
– wayne, Commented Mar 5, 2014 at 1:57
Where is selected_country set? Please post the complete code and its invocation — Bergi
– Bergi, Commented Mar 5, 2014 at 1:59
I have updated the post and it now contains my full .js file. I have two <select> fields in my php file one to select a country and the other a county depending on the country selected. What I what to do is set the default country in the <select> field depending on the variable $g_country. $g_country is a valid string "Republic of Ireland". — user1356029
– user1356029, Commented Mar 5, 2014 at 2:15
Update if i change country_arr[i] to country_arr[0] it works. Very weird but getting closer. Any ideas? — user1356029
– user1356029, Commented Mar 5, 2014 at 2:51

Jacob · Accepted Answer · 2014-03-05 02:01:11Z

1

The issue isn't the if statement, but that you have an error elsewhere. This is what's wrong:

option_str.options[option_str.length] = ...

option_str.length is probably not what you meant. Try:

option_str.options[option_str.options.length] = ...

...or better yet:

option_str.options.push(new Option(...));

Here's a working example.

edited Mar 5, 2014 at 2:01

answered Mar 5, 2014 at 1:55

Jacob

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