Javascript not reaching end of array

Question

Ive got a really strange problem with some javascript code that ive written. I have set this code to execute on load. The idea of it is to remove a value from a text field if it is listed in another field. Here is the code:

var diseases = document.getElementById("AffectedBy").value;  
        var diseasearray = diseases.split("-");  
        alert("disease array size: " + diseasearray.length);  
        for (i=0;i<diseasearray.length;i++)  
            if (diseases.match("-" + diseasearray[i]))  
                {  
                    diseasearray[i] = "-" + diseasearray[i];  
                    alert(diseasearray[i]);                           
                    document.getElementById("DiseaseNotSelected").value=document.getElementById("DiseaseNotSelected").value.replace(diseasearray[i],"")
                }

This code above gives an array size of 3 (1 blank, and 2 values) but when I display the values in the alert it only shows 2 values(1 blank, and 1 value)

This piece of code:

var foods = document.getElementById("FoodFor").value;  
        var foodarray = foods.split("-");  
        alert("food array size: " + foodarray.length);  
        for (i=0;i<foodarray.length;i++)  
            if (foods.match("-" + foodarray[i]))  
                {  
                    foodarray[i] = "-" + foodarray[i];  
                    alert(foodarray[i]);  
                    document.getElementById("FoodNotSelected").value=document.getElementById("FoodNotSelected").value.replace(foodarray[i],"")
                }

This code above gives an array size of 3 (1 blank, and 2 values) and when I display the values in the alert it only shows 3 values(1 blank, and 2 value).

Can anyone see a reason why the first code block only shows 2 items in the array as I cant see why and its really bugging me now.

Could you post the HTML code of AffectedBy and DiseaseNotSelected? Also, beware that whatever you pass into match will get turned into a regular expression. If that contains some special character, it might not match where you would expect it to (or vice versa). — Martijn
– Martijn, Commented Feb 24, 2011 at 21:13
Ok, A bit more detail, the first code block is analysing this string as AffectedBy: -Fin Rot-White Spot (Ich)-Gill Rot The result comes back as: -White Spot (Ich)-Test-Blue Sturgeon Test Disease but it should show -Test-Blue Sturgeon Test Disease. The second one analyses this as FoodFor: -Hikari Wheatgerm Sinking Pellet and returns -Tetrapond Sticks-New Food-New Food 2-New Food 3 which is correct as they are the other items. For these results the array sizes are (respectively) 4 and 2 — Stefan
– Stefan, Commented Feb 24, 2011 at 21:15
@martijn - I think you've hit the nail on the head, the only one it seems to play up with is WhiteSpot (Ich) is there a way I can get round this? — Stefan
– Stefan, Commented Feb 24, 2011 at 21:48

Kae Verens · Accepted Answer · 2011-02-24 21:06:30Z

4

the first one is running a match against a string starting with '-'.

I don't have your actual values, but let's say that the value of #AffectedBy is "test1-test2-test3".

the first alert will be 3, because the diseasearray will have three components (test1, test2, test3)

you then run through a loop (0, 1, 2).

The first one will fail, as there is no "-test1" in the string, but the other two will succeed, as there are "-test2" and "-test3" substrings.

answered Feb 24, 2011 at 21:06

Kae Verens

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1 Comment

Stefan Over a year ago

I've added more detail to the original question

Martijn · Accepted Answer · 2011-02-24 22:02:00Z

1

As I said in my comment above: beware that whatever you pass into match will get turned into a regular expression. If that contains some special character, it might not match where you would expect it to (or vice versa).

The string White Spot (Ich) will be turned into the regex /White Spot (Ich)/; which does not match White Spot (Ich) but does match White Spot Ich, since the parentheses are grouping operators in a regex.

Change the regular expression test

diseases.match("-" + diseasearray[i])

into the plain string comparison

diseases.indexOf("-" + diseasearray[i]) !== -1

and you should be set.

(I think. :-)

edited Feb 24, 2011 at 22:02

answered Feb 24, 2011 at 21:55

Martijn

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2 Comments

Stefan Over a year ago

You sir are an absolute legend. this has worked perfectly. I am a beginner to all of this so I am learning the javascript as I go along.

Martijn Over a year ago

@Stefan: Glad I could help. :-) In matters of Javascript, the MDC and Douglas Crockford are not to be missed.

ThorDozer · Accepted Answer · 2011-02-24 21:04:06Z

0

First, for the length you need to do for example foodarray.length -1. How many items do you have in your array (suppose to have)? We need more explanation

answered Feb 24, 2011 at 21:04

ThorDozer

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1 Comment

Stefan Over a year ago

ive added more detail to the original question now

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