Property 'find' does not exist on type 'Product[]？

import * as express from 'express'
import {Server} from 'ws'


const app = express()

export class Product {
    constructor(
        public id: number,
        public title: string,
        public price: number,
        public rating: number,
        public desc: string,
        public categories: Array<string>
    ) { }
}

export class Comment {
    constructor(
        public id: number,
        public productId: number,
        public timestamp: string,
        public user: string,
        public rating: number,
        public content: string
    ) {

    }
}

const products: Product[] = [
    new Product(1, '第一個(gè)商品', 1.99, 3.5, '這是第一個(gè)商品，我在學(xué)習(xí)慕課網(wǎng)Angular入門實(shí)戰(zhàn)時(shí)創(chuàng)建的', ['電子商品', '硬件設(shè)備']),
    new Product(2, '第二個(gè)商品', 2.99, 2.5, '這是第二個(gè)商品，我在學(xué)習(xí)慕課網(wǎng)Angular入門實(shí)戰(zhàn)時(shí)創(chuàng)建的', ['圖書']),
    new Product(3, '第三個(gè)商品', 3.99, 4.5, '這是第三個(gè)商品，我在學(xué)習(xí)慕課網(wǎng)Angular入門實(shí)戰(zhàn)時(shí)創(chuàng)建的', ['電子商品']),
    new Product(4, '第四個(gè)商品', 4.99, 1.5, '這是第四個(gè)商品，我在學(xué)習(xí)慕課網(wǎng)Angular入門實(shí)戰(zhàn)時(shí)創(chuàng)建的', ['硬件設(shè)備']),
    new Product(5, '第五個(gè)商品', 5.99, 3.5, '這是第五個(gè)商品，我在學(xué)習(xí)慕課網(wǎng)Angular入門實(shí)戰(zhàn)時(shí)創(chuàng)建的', ['電子商品', '硬件設(shè)備']),
    new Product(6, '第六個(gè)商品', 6.99, 2.5, '這是第六個(gè)商品，我在學(xué)習(xí)慕課網(wǎng)Angular入門實(shí)戰(zhàn)時(shí)創(chuàng)建的', ['圖書']),
]

const comments: Comment[] = [
    new Comment(1, 1, "2017-02-02 22:22:22", "張三", 3, "東西不錯(cuò)1"),
    new Comment(2, 1, "2017-02-02 22:22:22", "張三", 3, "東西不錯(cuò)2"),
    new Comment(3, 1, "2017-02-03 22:22:22", "張三", 3, "東西不錯(cuò)3"),
    new Comment(4, 1, "2017-02-04 22:22:22", "張三", 3, "東西不錯(cuò)4"),
    new Comment(5, 2, "2017-02-05 22:22:22", "張三", 3, "東西不錯(cuò)5"),
]

app.get('/',(req,res) => {
    res.send("hello express")
})

app.get('/api/products', (req,res)=> {
    let result = products
    let params = req.query;
    if(params.title){
        result = result.filter((p) => p.title.indexOf(params.title) !== -1)
    }

    if (params.price && result.length > 0) {
        result = result.filter((p) => p.price <= parseInt(params.price))
    }

    if (params.category !== "-1" && result.length > 0) {
        result = result.filter((p) => p.categories.indexOf(params.category) !== -1)
    }

    
    res.json(result)
})

app.get('api/comments/:id', (req, res) => {
    console.log(req.params.id)
    res.json(comments.filter((comment: Comment) => comment.productId == req.params.id))
})

app.get('/api/product/:id',(req,res) => {
    res.json(products.find((product)=>product.id==req.params.id))
})


const server = app.listen(8000, "localhost", ()=> {
    console.log("服務(wù)器已經(jīng)啟動(dòng)")
})

const wsServer = new Server({port:8085});
wsServer.on("connection", websocket => {
    websocket.send("這個(gè)消息是服務(wù)器主動(dòng)發(fā)送的"),
    websocket.on("message", message => {
        console.log("接收到消息"+ message)
    })
} )

編譯的時(shí)候報(bào)了個(gè)錯(cuò)

error TS2339: Property 'find' does not exist on type 'Product[]'.   

幫我說一下怎么改？謝謝了


git地址在https://github.com/yyccQQu/18ng2