var num = [1,2,3,4,5]
var sum=num.reduce(function(prev,cur,index,array){
return prev+cur
})
console.log(sum) //15
var num = [1,2,3,4,5]
var sum=num.reduce((pre,nex)=>pre+nex)
alert(sum)
var num = [1,2,3,4,5]
var sum=num.reduce(function(prev,cur,index,array){
return prev+cur
})
console.log(sum) //15
var num = [1,2,3,4,5]
var sum=num.reduce((pre,nex)=>pre+nex)
alert(sum)