Uncaught TypeError: test is not a function

Question

For some reason I get an error when I give the function a name..

However if I make it an anonymous function and assign it to a variable then I can call the function.

function test(){
    console.log(this)
}

test();

---

//************** 
// recursion 1
//************** 
var recursion = function(n){
    if(n==0){
        // console.log('yup');
        return 'success';
    }
    // console.log(n)
    return recursion(n - 1);
}

var x = recursion(10);

// console.log(x);

//************** 
// recursion 2
//************** 

var countDownFrom = function(x){
    if(x === 0){
        return true;
    }
    // console.log(x)
    return countDownFrom(x-1)
}

// console.log(countDownFrom(10))
//************** 
// fibonacci
//************** 

// console.time('fib')
function fibonacci(){
    var a = 0,
    b = 1,
    result = b;


    for(var i =0; i<100; i++){
        console.log(result);
        result = a + b;
        a=b;
        b=result;
    }
}

// console.log(fibonacci())
// console.timeEnd('fib')

//************** 
// removeDuplicate
//**************

console.time('dups')
function removeDuplicate(arr){
  var exists ={},
  outArr = [], 
  elm;

  for(var i =0; i<arr.length; i++){
    elm = arr[i];
    if(!exists[elm]){
      console.log(exists);
      outArr.push(elm);
      exists[elm] = true;
      console.log(exists);
      console.log(outArr);
      console.log(elm);
  }
}
return outArr;
}


removeDuplicate([1,3,3,3,1,5,6,7,8,1]);
console.timeEnd('dups')

//************** 
// mergeSorting
//**************
function mergeSortedArray(a, b){
  var merged = [], 
  aElm = a[0],
  bElm = b[0],
  i = 1,
  j = 1;

  if(a.length ==0)
    return b;
if(b.length ==0)
    return a;
  /* 
  if aElm or bElm exists we will insert to merged array
  (will go inside while loop)
   to insert: aElm exists and bElm doesn't exists
             or both exists and aElm < bElm
    this is the critical part of the example            
    */
    while(aElm || bElm){
       if((aElm && !bElm) || aElm < bElm){
         merged.push(aElm);
         aElm = a[i++];
     }   
     else {
         merged.push(bElm);
         bElm = b[j++];
     }
 }
 return merged;
}

//************** 
// swap number without temp
//**************

function swapNumb(a, b){
  console.log('before swap: ','a: ', a, 'b: ', b);
  b = b -a;
  a = a+ b;
  b = a-b;
  console.log('after swap: ','a: ', a, 'b: ', b);  
}

swapNumb(2, 3);

//************** 
// JS reverse string
//**************

function reverseString(str) {
    var newString = "",
    stringLength = str.length;

    for (var i = stringLength - 1; i >= 0; i--) {
        newString += str[i];
    }
    return newString;
}
var newString = reverseString('hello');
console.log(newString);

var test = "yoyo";
console.log(test += 'asdfa')

//************** 
// JS Reverse Word
//**************

function reverseWords(str){
 var rev = [], 
     wordLen = 0;
 for(var i = str.length-1; i>=0; i--){
   if(str[i]==' ' || i==0){
     rev.push(str.substr(i,wordLen+1));
     wordLen = 0;
   }
   else
     wordLen++;
 }
 return rev.join(' ');
}

var str = "lets go all day";
console.log(str.substr(11,5))
var s = reverseWords(str);
console.log(s);

//************** 
// JS Palindrome
//**************   


function isPalindrome(str){
  var i, len = str.length;
  for(i =0; i<len/2; i++){
    if (str[i]!== str[len -1 -i])
       return false;
  }
  return true;
}

isPalindrome('madam');
isPalindrome('toyota');

//************** 
// JS this
//**************  

function test(){
    console.log(this)
}

test();

Answer 1

This might be a hoisting issue. If you have more JS code above your code snippet, test might have been assigned to something else.

This will cause a TypeError because test will be a string by the time you call it:

// ... some code

var test = 'This is a test.';

// ... more code

function test() {
  console.log(this);
}

test();

This will work because test is assigned to a function right before you call it:

// ... some code

var test = 'This is a test.';

// ... more code

test = function () {
  console.log(this);
}

test();

In the first example, this is what the interpreter does, more or less:

1. Assign a function definition to test . (This happens first because it hoists function declarations above everything else)
2. Reassign test to be a string.
3. Invoke test , which is a string.

Second example:

1. Declare test with no value ( undefined ).
2. Assign test to a string.
3. Reassign test to a function.
4. Invoke test , which is a function.

Answer 2

It looks OK, the function prints an object when you call this inside the function

 function test() { console.log(this) } test() 

Answer 3

I just did a CTRL + F on your code and it seems that you already have a variable defined with the name of test in above scope. Please edit your code to remove the test variable declared above