Removing Values in Array using .splice() in Javascript

The problem is with this line:

if(arr[i]===false||null||0||undefined||NaN||""){...}

The correct way to compare for multiple values is:

if(arr[i]===false|| arr[i]=== null|| arr[i]===  0||arr[i] ===  undefined|| arr[i] ===  NaN|| arr[i]===  ""){ ..}

You can simplify it further as all values we need to filter naturally evaluates to false

if(!arr[i])

Reimplementation of your function with the index adjusted for splicing:

function bouncer(arr){
    for( var i = 0 ; i < arr.length ; i++ ){
        if(!arr[i]){
            arr.splice(i--,1);
        }
    }
    return arr;
}

A better way to do this with immutability is by using Array.filter

function bouncer(arr){
    return arr.filter((item) => (!!item));
}

You might want to read the javascript language syntax descriptions, again.

if(arr[i]===false||null||0||undefined||NaN||"") ...

means, if arr[i] is false, or null is true or 0 is true or undefined is true or NaN is true or "" is true. The first part depends on what arr[i] is, but the rest will all be false. That means we can simplify your statement, as written, to:

if (arr[i] === false) ...

Since the all the rest will always be false. But inferring what you want to do, you might want to say

if (arr[i] == false) ...

which will perform a looser, less rigorous comparison (i.e., it won't check the types of the elements being compared) and will test what I infer you want.

However, your logic has another problem: you are removing elements as you're iterating over the array, i is advancing as you are removing elements from under it. Another approach might be to build up the returned array (rather than modify the input array).

function bouncer(arr) {
  var r=[];
  for(i=0;i<arr.length;i++){
    if ( arr[i] )
      r.push(arr[i]);
  }
  return r;
}

Or better yet, use a method which is designed for the purpose of determining elements to keep (though it does not modify the original array, so you'll have to reassign it:

arr = arr.filter(function (elem) { return elem; });

mistakes:

1. Should be if(arr[i]===false||arr[i]===null||arr[i]===0||arr[i]===undefined||arr[i]===NaN||arr[i]==="")
2. Since NaN !== NaN, should use isNaN(arr[i])
3. if (...) { arr.splice(i,1); i--; // should minus one here! }