jumble.js

String.prototype.jumble=function(){
    var words=this.split(" ");
    var outputs=[];
    for(var i=0;i<words.length;i++){
        var word=words[i];
        var letters=word.split("");
        var output="";
        letters.pop();letters.shift();
        var k=letters.length;
        if(k==0){outputs.push(word);continue;};
        while(--k){
            var l=Math.floor(Math.random()*(k+1));
            var temp_k=letters[k];
            var temp_l=letters[l];
            letters[k]=temp_l;
            letters[l]=temp_k;
        };
        word=word.charAt(0)+letters.join("")+word.charAt(word.length-1);
        outputs.push(word);
    };
    return outputs.join(" ");
};

"some string to jumble".jumble(); // "smoe sitrng to jlmbue"