'for loop' and possible syntax error

Question

Here is my current javascript. I know that it worked until I added the 'for loop'. The point of the for loop is to switch letters. As it stands, its checking to see if groups of 3 are equal to one letter. I will fix that later, but I know there must be a syntax error, as the buttons don't fade as my mouse moves over them. I know this is a stupid question and I'll kick myself when I see the error, but I'm tired and can't find it for my life right now. Also, is this for loop a valid way of changing letters? Is that the correct way to set an array value to the new letter?

Here is the script.js:

    $(document).ready(function() {
    $('#button_translate').mouseenter(function() {
        $('#button_translate').fadeTo('fast', 1);
    });
    $('#button_translate').mouseleave(function() {
        $('#button_translate').fadeTo('fast', 0.7);
    });
    $('#button_clear').mouseenter(function() {
        $('#button_clear').fadeTo('fast', 1);
    });
    $('#button_clear').mouseleave(function() {
        $('#button_clear').fadeTo('fast', 0.7);
    });
    $('#button_translate').click(function() {
        var dna = $('input[name=dna]').val();
        var dna = dna.toUpperCase();
        function allBases(text) {  
            var bases = /^[ACGT]+$/;  
            if(text.match(bases)) {  
                var arr = text.match(/.{1,1}/g);
                /*document.write(arr + " is a DNA sequence.");*/
                for (var i = 0; i < (dna.length); i++) {
                    if (arr[i]==='A') {
                        arr[i]='U'
                    }else if (arr[i]==='C') {
                        arr[i]='G'
                    }else if (arr[i]==='G') {
                        arr[i]='C'
                    }else if (arr[i]==='T') {
                        arr[i]='U'
                    }else{
                        document.write(dna + " is not a real DNA sequence. Error Code 2");
                    }
                }
                document.write(dna + " is the translated mRNA strand!");
            }else{
                document.write(dna + " is not a real DNA sequence.");
            }  
        }

        allBases(dna);

    });
});

Should you be redeclaring the array elements. var arr[i]='U' becomes arr[i]='U'? — xagyg
– xagyg, Commented Aug 12, 2013 at 2:01

fvu · Accepted Answer · 2013-08-12 00:41:37Z

2

for (var i=0; i>=((dna.length) / 3); i++) {

you probably want the loop condition to be i less than dna.length

for (var i = 0; i < (dna.length/3); i++) {

edited Aug 12, 2013 at 0:41

fvu

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answered Aug 12, 2013 at 0:35

Leliel

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3 Comments

Leliel Over a year ago

what does it do? I note you've dropped the division by 3. was this intentional?

MacBoss123541 Over a year ago

I have intentionally dropped the division, and I'm using the "dna" string opposed to an array, and it still doesn't work, even if I only enter one letter in the text box.

Leliel Over a year ago

yes, you won't be able to access parts of a string with arr[index]. That's array access syntax, for a string, you'd have to use String replacement MDN reference

Arun P Johny · Accepted Answer · 2013-08-12 00:33:44Z

0

you have an unclosed ( in the for loop

for (var i=0; i>=(dna.length) / 3); i++) { // extra ( in i>=((dna.length) / 3)

answered Aug 12, 2013 at 0:33

Arun P Johny

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2 Comments

MacBoss123541 Over a year ago

but I want its length divided by 3, is the extra pair of parentheses un-needed? Does it confuse the program?

Arun P Johny Over a year ago

@RileyLloyd the extra ( is not needed because the expression will be processed based on operator precedence where . operator has higher precedence than >= operator

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