三元运算符如何比较 JavaScript 中的字符和数字？

Question

I had to find maximum in array so I wrote a function which used for loop while also using ternary operator and I noticed that just reversing the direction of loop changes the output plus the output is also different if I use if-else. Moreover, changing the position of 'a' in the array also changes the output.

 const array2 = ['a', 3, 4, 2]; function biggestNumberInArray(arr) { let max=0; for (let i = 0; i < arr.length; i++) { max = max>arr[i]?max:arr[i]; } return max; } function biggestNumberInArray2(arr) { let max=0; for (let i = arr.length - 1; i >= 0; i--) { max = max>arr[i]?max:arr[i]; } return max; } console.log(biggestNumberInArray(array2)); console.log(biggestNumberInArray2(array2));

When running the first function output is 4

When running the second function output is 'a'

Answer 1

If you step through the debugger and look at the comparisions ... you'll see that comparing 'a' with any number is always false.

That's why it seems to "work" in one direction, but not the other.

Specifically:

When comparing a string with a number, JavaScript will convert the string to a number when doing the comparison. An empty string converts to 0. A non-numeric string converts to NaN which is always false . When comparing two strings, "2" will be greater than "12", because (alphabetically) 1 is less than 2.

Answer 2

Because string 'a' and integers 2,3,4 are incomparable. Therefore it always returns false

In your first function, it returns 4 because 'a' is compared first and returns false , then max is assigned 3

In the second function it returns 'a' because 'a' is compared last.

You can check if the string can be converted to number using Number() or parseInt()

 const arr = ['a', 3, 4, 2]; function biggestNumberInArray2(arr) { let max=0; for (let i = arr.length - 1; i >= 0; i--) { const comparable = Number(arr[i]) || -99 max = max > comparable ? max : comparable; } return max; } console.log(biggestNumberInArray2(arr))