[JavaScript] JS finds the sum of the closed interval [min,max]

Find the sum of the closed interval [min,max]

An interval refers to a set that contains all the real numbers between two specific real numbers, and may also contain the two real numbers at the same time.

• The closed interval [10,20] means that {X|10<=X<=20}it contains 10 and 20
• The open interval (10, 20) means {X|10<=X<=20}that 10 and 20 are not included
  

 function sum(min,max){
    
    
     console.log(new Date().getTime());
     var sum=0, flag=(max-min)%2;
     if(flag){
    
    //点集个数为双数
         sum=(max-min+1)*((max+min)/2) 
     }else{
    
    //点集个数为单数
         sum=(max+min)*((max-min+1)/2)
     }
     console.log(new Date().getTime());
     
     return sum
 } 

 console.log(sum(0,101000))

 function sum1(min,max){
    
    
     console.log(new Date().getTime());
     var arr=[],sum=0;
     for(let i=min;i<=max;i++){
    
    
         arr.push(i)
     }
     sum=eval(arr.join('+'))   
     console.log(new Date().getTime());
     return sum
 }
 console.log(sum1(0,101000))