我一直在尝试使用Node.js,Express.js和MongoDB创建一个简单的站点.我是这些技术的新手,并且在设置数据库时遇到了问题以下是我的index.js文件中的代码片段:
var http = require('http'),
express = require('express'),
path = require('path'),
MongoClient = require('mongodb').MongoClient,
Server = require('mongodb').Server,
CollectionDriver = require('./collectionDriver').CollectionDriver;
var app = express();
app.set('port', process.env.PORT || 3000);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
var mongoHost = 'localHost';
var mongoPort = 27017;
var collectionDriver;
var mongoClient = new MongoClient(new Server(mongoHost, mongoPort));
mongoClient.open(function(err, mongoClient) {
if (!mongoClient) {
console.error("Error! Exiting... Must start MongoDB first");
process.exit(1);
}
var db = mongoClient.db("MyDatabase");
collectionDriver = new CollectionDriver(db);
});
在我尝试node index.js在终端中运行后,它会说以下内容:
js-bson: Failed …我正在尝试使用clip()画布中的函数来创建这种效果，如图所示：有一个背景图像，当鼠标悬停在其上时，会显示部分图像。我让它作为一个圆圈工作，但我想要这种渐变效果，你可以看到图片。我该如何实现这一目标？
<!DOCTYPE HTML>
<html>
<head>
<link rel="stylesheet" type="text/css" href="./assets/stylesheet/normalize.css">
<link rel="stylesheet" type="text/css" href="./assets/stylesheet/style.css">
</head>
<body>
<canvas id="canvas" width="2000" height="1200"></canvas>
<script>
var can = document.getElementById('canvas');
var ctx = can.getContext('2d');
can.addEventListener('mousemove', function(e) {
var mouse = getMouse(e, can);
redraw(mouse);
}, false);
function redraw(mouse) {
console.log('a');
can.width = can.width;
ctx.canvas.width = window.innerWidth;
ctx.canvas.height = window.innerHeight;
ctx.drawImage(img, 0, 0);
ctx.beginPath();
ctx.rect(0,0,2000,1200);
ctx.arc(mouse.x, mouse.y, 200, 0, Math.PI*2, true)
ctx.clip();
ctx.fillRect(0,0,2000,1200);
}
var img = new Image();
img.onload = function() {
redraw({x: 0, y: …