Mt srting is not shuffled WHY?

Question

String.prototype.shuffle = function(){
var tmp,cur,top = this.length;
if(top) while(--top){
cur = Math.floor(Math.random() * (top + 1));
tmp = this[cur];
this[cur] = this[top];
this[top] = tmp;
}
return this;
}

randomWord = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklm...
console.log(randomWord.substr(0,8));

//output
ABCDEFGH

why it is not shuffled

Leo D · Accepted Answer

I'm not an expert on JavaScript honestly, but the primary reason why I believe this is happening is because I believe that strings are immutable.

Now that last part of the second to last line got caught off because of Yahoo Answer's cut off point, but I imagine that you used .shuffle() at the end of the two alphabet string literal. If you didn't, you have to remember to do this. The immutability of strings means that you can't actually shuffle the string but you have to instead shuffle a copy and return it.

About the copy, the copy can't be another string, which I believe is what you did. You need to create a character array. You can do that by doing some thing like this { var carr = this.split(""); }. This will split the String into a character array split after every character. (toCharArray should probably be its own function, but I don't know how worth it this added modularity would be in JS.) Operate on the character array { carr } instead of { this }.

Once you have finished, return carr.join("") instead of { this }. That's it :)

Remember that if { text } is your string, calling { shuffle() } on it won't shuffle the string, but return a shuffled copy of the string. The way you could get around that is by creating a mutable string container (like a string buffer), but again that might not be worth it.

John · Answer

You can't modify a single character in a string: 
this[cur] = this[top]; 
this[top] = tmp;

But you can turn the string into an array and then modify the bits in the array, and then join them.

Try this: http://pastebin.com/EFkBbQUc

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Mt srting is not shuffled WHY?

2 Answers