JS中數(shù)組的迭代方法：filter、reduce、every、some

let a = [1, 2, 3];
a = a.reduce(function (prev, next) {
 return prev + next // 1+2+3 = 6
})

let a = [1, 2, 3];
a = a.filter(function (value, i) {
 return value > 2 
})
console.log(a) // 3

let a = [1, 2, 3];
a = a.every(function (value, i) {
 return value > 2 
})
console.log(a) // false

let a = [1, 2, 3];
a = a.every(function (value, i) {
 return value > 2 
})
console.log(a) // true