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Asked: 2026-06-08T08:27:08+00:00

I need to write some JavaScript functionality that analyses an address block and displays

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I need to write some JavaScript functionality that analyses an address block and displays an error
message if the postcode in this delivery address is within one of a given list (eg. going to be affected by
the Olympics). I have used indexOf to match the contents of the address block against a list
of affected postcodes and this works fine.

However the problem occurs because a postcode starting with DW3 which is not affected will
display the affected message because the indexOf is picking up W3. As you can see in my
code below i have tried to match on a space preceeding the postcode
i.e. ” DW3″ but this doesn’t work at all and i have no idea why.

Perhaps regular expressions is a better way to match this pattern, unfortunately
I am terrible at regex, so can anyone help with this?

An example address would be:

<address>Mr Jim Smith<br>
    Flat, 4 Spring Lane<br>
    EASTLEIGH<br>
    DW3 6LS<br>
    United Kingdom</address>

here is the JavaScript:

var AFFECTED_POSTCODES = ["DT1","DT10","DT11","DT2","DT3","DT4","DT5","DT6","DT8","DT9","E1","E10","E11","E13","E14","E15","E16","E18","E1W","E3","E6","E9","EC1A","EC2N","EC2R","EC2V","EC2Y","EC3M","EC3N","EC3R","EC3V","EC4","EC4M","EC4N","EC4R","EC4V","EC4Y","GU22","GU23","GU4","GU5","HA9","IG1","IG11","IG4","IG7","IG8","KT1","KT10","KT11","KT12","KT13","KT14","KT18","KT2","KT20","KT22","KT24","KT6","KT7","KT8","NW1","NW10","NW8","RH4","RH5","RM13","RM15","RM9","SE1","SE10","SE11","SE18","SE3","SE7","SL0","SL3","SW10","SW11","SW13","SW15","SW18","SW19","SW1A","SW1E","SW1H","SW1P","SW1V","SW1W","SW1X","SW1Y","SW3","SW5","SW6","SW7","SW8","TW1","TW10","TW11","TW19","TW5","TW6","TW7","TW8","TW9","UB3","UB7","W10","W11","W12","W14","W1B","W1C","W1G","W1H","W1J","W1K","W1T","W1U","W1W","W2","W3","W4","W5","W6","W7","W9","WC1A","WC1B","WC1E","WC1H","WC1N","WC1R","WC1V","WC2A","WC2B","WC2E","WC2N","WC2R"];
function checkPostcode(e){
    var isAffected = false,
        field = $('#delivery_details_wrapper address'),
        fieldText = $(field).text();
    for (var i=0; i<AFFECTED_POSTCODES.length; i++){
        var patt = ' ' + AFFECTED_POSTCODES[i];
        if (fieldText.indexOf(patt) !== -1) {
            isAffected = true;
        }
    }
    if (isAffected) {
        if ($('.warning').length === 0) {
            field.after('<p class="warning" style="margin-top: 10px; clear: both;">* Delivery to this postcode may be affected by the Olympics. For more info click <a href="'+ Arcadia.Loader.rootPath +'lib/html/olympic_message.html" class="lightbox" rel="lightbox({innerWidth: 600, innerHeight: 300})" title="Click here for postcodes that may be affected by the olympics">here</a></p>');
        }
    } else {
        $('.warning').remove();
    }
}
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1 Answer

  1. Editorial Team

    A regular expression would indeed be better, being more concise and more efficient (the expression will compile to an optimal matching automaton). It would also be quite simple.

    var alternation = AFFECTED_POSTCODES.join('|');
var r = new RegExp('\\b(' + alternation + ')\\b');
var isAffected = r.test(fieldText);

    Here the \b means match a word boundary, which will deal with your sub-string problem.
    You may even just write out the postcodes in a regex literal – /\b(DT1|DT10...)\b/ – if you don’t need the array anywhere else.

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