[ JS 常見問題 ] Time difference in Nodejs?

Source From Here 
Question 
Im trying to figure out a way to get the time difference in seconds between two dates. For example, difference in seconds between: 

Start 2013-5-11 8:37:18 
End 2013-5-11 10:37:18

How-To 
You can leverage moment module: 

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1. var moment = require('moment')  
2. var startDate = moment('2013-5-11 8:37:18', 'YYYY-M-DD HH:mm:ss')  
3. var endDate = moment('2013-5-11 10:37:18', 'YYYY-M-DD HH:mm:ss')  
4. var secondsDiff = endDate.diff(startDate, 'seconds')  
5. console.log(secondsDiff) // Output 7200  

More usage on moment module: 

> st = moment() 
moment("2019-02-19T19:06:46.633") 
> et = moment() 
moment("2019-02-19T19:06:52.655") 
> et.diff(st, 'seconds') 
6 
> var now = new Date() 
> now 
2019-02-19T11:07:25.880Z 
> now_in_moment = moment(now) // Transform Date object into moment object 
moment("2019-02-19T19:07:25.880") 
> var now_as_date = now_in_moment.toDate() // Transform moment object back to Date object 
> now_as_date 
2019-02-19T11:07:25.880Z 
> now_as_date.constructor.name 
'Date'

Supplement 
* FAQ - How to format a JavaScript date 
* FAQ - Moment.js transform to date object 
* W3CSchool - JavaScript Date Reference 
* npm - moment: A lightweight JavaScript date librar...ulating, and formatting dates. 

# npm install -S moment

[ 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