How to calculate the number in an array by using function?

Question

for example, an array include {14,23,5,30}
how to use a function to show 30-23=7?

I tried this but it is not correct:
function calculate(array1, array2){
var newArray [];
newArray[0]=difference(newArray[3],newArray[2]);
}

Answer 1

array = [15,23,5,30];

function subtract(){
var x = array[3];
var y = array[1];
var ans = x - y;
console.log(ans)
};
subtract()

Is this what you want.....

Answer 2

If you want to display "30-23=7", then you need to return a string...

function calculate(array1) {
var calculation;
calculation = array1[3] - array1[1];

return array1[3].toString() + '-' + array1[1].toString() + '=' + calculation;
}