javascript - How to sort an array of integers correctly

Trying to get the highest and lowest value from an array that I know will contain only integers seems to be harder than I thought.

var numArray = [140000, 104, 99];
numArray = numArray.sort();
alert(numArray)

I'd expect this to show 99, 104, 140000. Instead it shows 104, 140000, 99. So it seems the sort is handling the values as strings.

Is there a way to get the sort function to actually sort on integer value?

Answer

By default, the sort method sorts elements alphabetically. To sort numerically just add a new method which handles numeric sorts (sortNumber, shown below) -

function sortNumber(a, b) {
  return a - b;
}

var numArray = [140000, 104, 99];
numArray.sort(sortNumber);

console.log(numArray);

In ES6, you can simplify this with arrow functions:

numArray.sort((a, b) => a - b); // For ascending sort
numArray.sort((a, b) => b - a); // For descending sort

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Documentation:

Mozilla Array.prototype.sort() recommends this compare function for arrays that don't contain Infinity or NaN. (Because Inf - Inf is NaN, not 0).

Also examples of sorting objects by key.