The three functions traverse each element in the array, very similar
The structures are:
函数((参数)=>{
return ...
})
But there are some subtle differences:
The return of filter is a judgment condition, it must be a boolean value, and finally returns a new array
The return of map is an expression, which performs related operations on the value of each element of the array, and finally returns a new array
The return of reduce is also an expression, but each step adds the value of the current element to the calculation result of the previous step
var numbers = [65, 44, 12, 4];
numbers.reduce(function getSum(total, num) {
return total + num;
})
//结果125，默认初始值为0
numbers.reduce(function getSum(total, num) {
return total + num;
},10)
//结果135，因为设置了初始值为10