Question

I have a small string and a fixed seed and I am trying to shuffle all the string elements with the given seed so its repeatable.

Here is the code I have:

function shufff(strin,seed){
    var tem;
    var j;
    var tt = strin.length;
    for(var i=0; i<tt; i++){
        j = ( seed % (i+1) + i) % tt;
        tem=strin[i];
        strin[i] = strin[j];
        strin[j] = tem;
    }
    return strin;
}

var tom='tomollow';
alert(shufff(tom,6543));

This returns the original string back with no shuffling.

What am I doing wrong?

Answer 1

Array-style access to individual characters in JavaScript strings is read only. (And not supported at all in older browsers.)

A minimal change to your code to get it to work would be to convert your string to an array for processing and then convert it back to a string when you return it:

function shufff(strin,seed){
    strin = strin.split("");
    var tem;
    var j;
    var tt = strin.length;
    for(var i=0; i<tt; i++){
        j = ( seed % (i+1) + i) % tt;
        tem=strin[i];
        strin[i] = strin[j];
        strin[j] = tem;
    }
    return strin.join("");
}

Working demo: http://jsfiddle.net/fcKDN/