Why is math.max() returning NaN on an array of integers?

I am trying to get the highest number from a simple array:

data = [4, 2, 6, 1, 3, 7, 5, 3];

alert(Math.max(data));

I have read that if even one of the values in the array can't be converted to number, it will return NaN, but in my case, I have double-checked with typeof to make sure they are all numbers, so what can be my problem?

Answers:

Answer

The reason why your code doesn't work is because Math.max is expecting each parameter to be a valid number. This is indicated in the documentation as follows:

If at least one of arguments cannot be converted to a number, the result is NaN.

In your instance you are only providing 1 argument, and that 1 value is an array not a number (it doesn't go as far as checking what is in an array, it just stops at knowing it isn't a valid number).

One possible solution is to explicitly call the function by passing an array of arguments. Like so:

Math.max.apply(Math, data);

What this effectively does is the same as if you manually specified each argument without an array:

Math.max(4, 2, 6, 1, 3, 7, 5, 3);

And as you can see, each argument is now a valid number, so it will work as expected.

Answer

if you see doc for Math.max you can see next description

Because max() is a static method of Math, you always use it as Math.max(), rather than as a method of a Math object you created (Math is not a constructor).

If no arguments are given, the result is -Infinity.

If at least one of arguments cannot be converted to a number, the result is NaN.

When you call Math.max with array parameter like

Math.max([1,2,3])

you call this function with one parameter - [1,2,3] and javascript try convert it to number and get ("1,2,3" -> NaN) fail.
So result as expected - NaN

NOTE: if array with just one number - all work correctly

 Math.max([23]) // return 23

because [23] -> "23" -> 23 and covert to Number is done.


If you want get max element from array you should use apply function, like

Math.max.apply(Math,[1,2,3])

or you can use the new spread operator

Math.max(...[1,2,3])
Answer

It's not working because you are passing an array as the parameter instead of comma separated numbers. Try spreading the array like this:

data = [4, 2, 6, 1, 3, 7, 5, 3];    
alert(Math.max(...data));
Answer

If you have to use the Math.max function and one number of the array might be undefined, you could use:

x = Math.max(undefined || 0, 5)
console.log(x) // prints 5

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