function shuffle(str, l){ //STRING TO BE SHUFFLED AND ITS NUMBER OF CHARACTER INCLUDING SPACES
var x = []; //BLANK ARRAY UNTIL 1ST "FOR LOOP"
var s = ''; //BLANK STRING UNTIL 2ND "FOR LOOP"

for(i=0; i<l; i++){
x[i] = i; //PUTS EACH LETTER OF THE STRING IN AN ARRAY
}

for(i=0; i<l; i++){
m = l-i; //DECREASES ARRAY SIZE THOUGHOUT THIS "FOR LOOP"
r = Math.floor(Math.random()*m); //SELECTS A RANDOM LETTER FROM THE ARRAY
d = x[r]; //RANDOM LETTER
s += str[d]; //SHUFFLED STRING
x.splice(r, 1); //DELETES THE SELECTED CHARACTER FROM THE ARRAY TO PREVENT REPEATS
}
$("#shuffle").html(s); //SHUFFLED STRING DISPLAYED IN HTML
}
<input id="str" onKeyUp="shuffle(this.value, this.value.length)"><br>
<span id="shuffle"></span>
</body>
</html>

function shuffle(str, l){ //STRING TO BE SHUFFLED AND ITS NUMBER OF CHARACTER INCLUDING SPACES
var x = []; //BLANK ARRAY UNTIL 1ST "FOR LOOP"
var s = ''; //BLANK STRING UNTIL 2ND "FOR LOOP"

for(i=0; i<l; i++){
x[i] = i; //PUTS EACH LETTER OF THE STRING IN AN ARRAY
}

for(i=0; i<l; i++){
m = l-i; //DECREASES ARRAY SIZE THOUGHOUT THIS "FOR LOOP"
r = Math.floor(Math.random()*m); //SELECTS A RANDOM LETTER FROM THE ARRAY
d = x[r]; //RANDOM LETTER
s += str[d]; //SHUFFLED STRING
x.splice(r, 1); //DELETES THE SELECTED CHARACTER FROM THE ARRAY TO PREVENT REPEATS
}
document.getElementById("#shuffle").innerHTML = s; //SHUFFLED STRING DISPLAYED IN HTML
}
<input id="str" onKeyUp="shuffle(this.value, this.value.length)"><br>
<span id="shuffle"></span>
</body>
</html>