Javascript中的高阶函数是什么

//map() and reduce()
let nums = [1, 2, 3, 4]
let addOne = nums.map((i) => i+1) // [2,3,4,5]
let combined = nums.reduce((res, cur) => res+=cur, 0) // 10

//normal version
let numbers = [1, 2, 3, 4]; 

const squares = (nums) => {
    let result = [];
    for(let i of nums) {
        result.push(i*i);
    }
    return result;
}

const addThree = (nums) => {
    let result = [];
    for(let i of nums) {
        result.push(i+3);
    }
    return result;
}
squares(numbers) // [1,4,9,16]
addThree(numbers) // [4,5,6,7]

//higher-order function version
let numbers = [1, 2, 3, 4]; 

const applyAll = (func, nums) => {
    let result = [];
    for(let i of nums) {
        result.push(func(i));
    }
    return result;
}

applyAll((i) => i*i, numbers) // [1,4,9,16]
applyAll((i) => i+3, numbers) // [4,5,6,7]

//you can chain filter -> map -> reduce
let numbers = [1, 2, 3, 4];
let result = numbers
    .filter(i => i%2===0)
    .map(i => i*2)
    .reduce((res, cur) => res+=cur, 0); // 12