[ JS 常見問題 ] How to sort an array of integers correctly

Source From Here 
Question 
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: 

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1. var numArray = [140000, 104, 99];  
2. numArray = numArray.sort();  
3. 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? 

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

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1. function sortNumber(a,b) {  
2.     return a - b;  
3. }  
4.       
5. var numArray = [140000, 104, 99];  
6. numArray.sort(sortNumber);  
7. alert(numArray.join(","));  

You can use ES6 arrow functions: 

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