Javascript Array Index Minus One

Question

Is it allowed to do something like Array[i - 1] in javascript? Assuming that i and i-1 are proper indexes of the Array.

I am wondering because it seems to give me errors but I don't know if the error is how I refer to indexes.

Furthermore, is it possible to do something like Array[Array.length - 1]?

The actual error is with this:

input = input.split('\n');
    for (var i = 1; i < input.length; i++){
        for (var j = 0; j < input[i].length; j++){
            process.stdout.write(input[i][j]);
            process.stdout.write(input[i][j - 1]);
            process.stdout.write(input[i][input[i].length - 1 - j]);
            process.stdout.write(input[i][input[i].length - j]);
          if (input[i][j] - input[i][j - 1] !== input[i][input[i].length - 1 - j] - input[i][input[i].length - j]){

          }  
        }

    }

Of the process.stdout.write statements, only the first outputs anything.

Yes. You can put any sort of expression you want inside [ ] so long as it evaluates to a number or a string. Post your actual code and the actual errors you're getting. — Pointy
– Pointy, Commented Oct 7, 2015 at 16:22
What "errors" are you getting? You can put any expression you want inside the []. — gen_Eric
– gen_Eric, Commented Oct 7, 2015 at 16:22
Yes, it's possible to use a.length - 1 as index to the array, in fact it is used to get the last element from array — Tushar
– Tushar, Commented Oct 7, 2015 at 16:24
Try avoiding plain yes/no questions. Add your code and errors to make your question more valuable. — m02ph3u5
– m02ph3u5, Commented Oct 7, 2015 at 16:35

Jonas · Accepted Answer · 2015-10-07 18:21:46Z

2

Yes, it`s possible.

See here: https://jsfiddle.net/hca4cecc/

var myObj = [1, 2, 3, 4, 5];
alert(myObj[2-1+3]);

Edit: With your updated information: There is a bug. The [j-1] is -1 in the first loop and your code should crash.

edited Oct 7, 2015 at 18:21

answered Oct 7, 2015 at 16:37

Jonas

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