We're building a web game where everybody wins and we are all friends forever.

It's simple—you click on one of three boxes to see what nice thing you've won. You always win something nice. Because we love you.

Here's what we have so far. Something's going wrong though. Can you tell what it is?

  
<button id="btn-0">Button 1!</button>
<button id="btn-1">Button 2!</button>
<button id="btn-2">Button 3!</button>

<script type="text/javascript">
    var prizes = ['A Unicorn!', 'A Hug!', 'Fresh Laundry!'];
    for (var btnNum = 0; btnNum < prizes.length; btnNum++) {
        // for each of our buttons, when the user clicks it...
        document.getElementById('btn-' + btnNum).onclick = function() {
            // tell her what she's won!
            alert(prizes[btnNum]);
        };
    }
</script>

try bad code

Reference: https://www.interviewcake.com/question/javascript/js-whats-wrong?

Solution:

  
<button id="btn-0">Button 1!</button>
<button id="btn-1">Button 2!</button>
<button id="btn-2">Button 3!</button>

<script type="text/javascript">
    var prizes = ['A Unicorn!', 'A Hug!', 'Fresh Laundry!'];
    for (var btnNum = 0; btnNum < prizes.length; btnNum++) {
        // for each of our buttons, when the user clicks it...
        bindClick(btnNum);
    }
    function bindClick(btnNum){
     document.getElementById('btn-' + btnNum).onclick = function() {
            // tell her what she's won!
            alert(prizes[btnNum]);
        };
    }
</script>

try solution

Write a function for doing an in-place shuffle of an array.
The shuffle must be "uniform," meaning each item in the original array must have the same probability of ending up in each spot in the final array.

Assume that you have a function getRandom(floor, ceiling) for getting a random integer that is >= floor and <= ceiling.

  
function getRandom(floor, ceiling){
   // console.log('getRandom floor:'+floor+' ceiling:'+ceiling);
   return  parseInt(floor) + parseInt( Math.random()*(ceiling - floor));
}
function swapInPlace(array,i,k){
    //console.log('swap i:'+i+' k:'+k);
 var v1 = array[i];
 var v2 = array[k];
 array[i] = v2;
 array[k] = v1;
}
function shuffleInPlace(array) {
    var floor = 0, ceiling = array.length;
    for(var i in array){
        var k = getRandom(i, ceiling)
  swapInPlace(array,i,k);
    }
}
var array = ['a','b','c'];
console.log('original array: '+array);
shuffleInPlace(array);
console.log('shuffled array: '+array);

https://www.interviewcake.com/question/java/shuffle

You're working with an intern that keeps coming to you with JavaScript code that won't run because the braces, brackets, and parentheses are off. To save you both some time, you decide to write a braces/brackets/parentheses validator.

Let's say:

• '(', '{', '[' are called "openers."
• ')', '}', ']' are called "closers."

Write an efficient function that tells us whether or not an input string's openers and closers are properly nested.

Examples:

• "{ [ ] ( ) }" should return true
• "{ [ ( ] ) }" should return false
• "{ [ }" should return false

ref: https://www.interviewcake.com/question/javascript/bracket-validator

  
var openers = ['(', '{', '['];
var closers = [')', '}', ']'];
function braces_brackets_parentheses_validator(code) {
    var stack = [];
    for(var i in code){
        index = openers.indexOf(code[i]);
        if(index >= 0){
            //console.log('push:'+code[i]);
            stack.push(code[i]);
        }else{
            index = closers.indexOf(code[i]);
            if(index >= 0){
                if(stack[stack.length-1] != openers[index]){
                    console.log('opener:"'+stack[stack.length -1]+'" unexpected closer:"'+closers[index]+'" at index:'+i);
                    return false;
                }
                //console.log('pop:'+stack[stack.length -1]);
                stack.pop();
            }
        }
    }
        
    return true;
}

// run your function through some test cases here
// remember: debugging is half the battle!
console.log(braces_brackets_parentheses_validator('{ [ ] ( ) }'));
console.log(braces_brackets_parentheses_validator('{ [ ( ] ) }'));
console.log(braces_brackets_parentheses_validator('{ [ }'));