Why does this Javascript function always return true?

Question

I built a function every that should iterate over an array and return true if the action (for ex. element < 10) performed on all the elements is true . Here's my code:

function every(array, action) {
  var trueOrFalse = true
  for (var i = 0; i < array.length; i++)  
    trueOrFalse = trueOrFalse && action(array[i]);
  if (trueOrFalse = true) return true;
  else  return;
}
array1 = [1,2,3,4,5,6,7,8,9,10,11]
console.log(every(array1, function(element) {
  return element < 10 
}))

I don't see anything wrong. With array1 it returns true even if it contains numbers > 10. Where's the problem?

Thanks

Answer 1

if (trueOrFalse = true) return true; 

应该

if (trueOrFalse == true) return true;

Answer 2

You need to evaluate trueOrFalse is equal to true For which you need the double equals

if (trueOrFalse == true) return true;

Other wise you'll just be making the value of trueOrFalse the same as true

Bonus points:

 if (trueOrFalse === true) return true;

Using three equal signs is evaluating exactly the same type and value. That isn't required here but is useful to know.

Answer 3

Your condition is using an incorrect operator, you should be using the == operator.

You can use if (trueOrFalse == true) return true;

OR

you can write it as if (trueOrFalse) return true; which will still evaluate it as if( true )

Answer 4

You can remove the if statement and rely on good old boolean algebra!

function every(array, action) {
  var trueOrFalse = true
  for (var i = 0; i < array.length; i++)  
    trueOrFalse = trueOrFalse && action(array[i]);
  return trueOrFalse;
}
array1 = [1,2,3,4,5,6,7,8,9,10,11]
console.log(every(array1, el => el < 10));