var items = [5, 10, 15];
var reducer = function minus(minusSum, item) {
? ? return minusSum - item;
}
var total = items.reduce(reducer, 61);
console.log(total); // 31

var items = [5, 10, 15];
var reducer = function minus(minusSum, item) {
? ? minusSum.sum = minusSum.sum - item;
? ? return minusSum;
}
var total = items.reduce(reducer, {sum: 61});
console.log(total); // {sum: 31}

var goodList = [
? ? {
? ? ? ? good: 'paper',
? ? ? ? price: 12
? ? },
? ? {
? ? ? ? good: 'book',
? ? ? ? price: 58
? ? },
? ? {
? ? ? ? good: 'CD',
? ? ? ? price: 15
? ? } ? ? ??
]

var count = goodList.reduce(function(prev, cur) {
? ? return cur.price + prev;
}, 0);
console.log(count); // 85

var count = goodList.reduce(function(prev, cur) {
? ? return cur.price + prev;
}, -10);
console.log(count); // 75

var goodList = [
? ? {
? ? ? ? good: 'paper',
? ? ? ? price: 12
? ? },
? ? {
? ? ? ? good: 'book',
? ? ? ? price: 58
? ? },
? ? {
? ? ? ? good: 'CD',
? ? ? ? price: 15
? ? } ? ? ??
];

var dis = {
? ? paper: 0.5,
? ? book: 0.8,
? ? CD: 0.2
}

var count = goodList.reduce(function(prev, cur) {
? ? return cur.price + prev;
}, -10);

var qcount = goodList.reduce(function(prev, cur) {
? ? return cur.price * dis[cur.good] + prev;
}, 0);

console.log(count, qcount); // 75 55.400000000000006

var arrString = 'fghffgaga';
var strArr = arrString.split('');
var rel = {};
var count = 1;
for (var i = 0; i < strArr.length; i++) {
? ? for (var j = i + 1; j < strArr.length; j++) {
? ? ? ? if (strArr[i] == strArr[j]) {
? ? ? ? ? ? count++;
? ? ? ? ? ? strArr.splice(j, 1);
? ? ? ? ? ? j = j - 1; ? ? ? ? ? ? ?
? ? ? ? }

? ? }
? ? var qcount = count;
? ? count = 1;
? ? rel[strArr[i]] = qcount; ? ?
}
console.log(rel); // {f: 3, g: 3, h: 1, a: 2}

var arrString = 'fghffgaga';
var rel = arrString.split('').reduce(function(res, cur) {
? res[cur] ? res[cur] ++ : res[cur] = 1
? return res;
}, {})
console.log(rel); // {f: 3, g: 3, h: 1, a: 2}

var arr = [1, 2].reduce(function(res, cur) {?
? res.push(cur + '');?
? return res;?
}, []);
console.log(arr); // ["1", "2"]