随机应变 ABCD: Always Be Coding and … : хороший
public class test
{
public static void main(String[] args)
{
System.out.println("Hello\nWorld!");
}
}
print and println
public class test
{
public static void main(String[] args)
{
System.out.print(3);
System.out.println(4 + 5);
}
}
compile error
public class test
{
public static void main(String[] args)
{
System.ouch.println(4 + 5);
}
}
The reason to use big data is it’s too big to store in one machine.Challenges with big data is data is created fast and data from different source in various formats.
Hadoop
Store in HDFS
process with MAPREDUCE
Hadoop ecosystem
pig, hive … select * from
mapreduce, impala, hbase
HDFS <- sqoop, flume
Hue, oozie, mahout
Cloudera is a distribution of Hadoop(CDH)
Hadoop picks three node as random.
javascript test library
https://jasmine.github.io/
describe('Address Book', function(){
it('should be able to add a contact', function(){
var addressBook = new AddressBook(),
thisContact = new Contact();
addressBook.addContact(thisContact);
expect(addressBook.getContact(0)).toBe(thisContact);
});
});
describe('Address Book', function(){
it('should be able to add a contact', function(){
var addressBook = new AddressBook(),
thisContact = new Contact();
addressBook.addContact(thisContact);
expect(addressBook.getContact(0)).toBe(thisContact);
});
it('should be able to delete a contact', function(){
var addressBook = new AddressBook(),
thisContact = new Contact();
addressBook.addContact(thisContact);
addressBook.deleteContact(0);
expect(addressBook.getContact(0)).not.toBeDefine();
});
});
/*
After you have changed the settings at "Your code goes here",
run this with one of these options:
"grunt" alone creates a new, completed images directory
"grunt clean" removes the images directory
"grunt responsive_images" re-processes images without removing the old ones
*/
module.exports = function(grunt) {
grunt.initConfig({
responsive_images: {
dev: {
options: {
engine: 'im',
sizes: [{
/*
Change these:
width: ,
suffix: ,
quality:
*/
}]
},
/*
You don't need to change this part if you don't change
the directory structure.
*/
files: [{
expand: true,
src: ['*.{gif,jpg,png}'],
cwd: 'images_src/',
dest: 'images/'
}]
}
},
/* Clear out the images directory if it exists */
clean: {
dev: {
src: ['images'],
},
},
/* Generate the images directory if it is missing */
mkdir: {
dev: {
options: {
create: ['images']
},
},
},
/* Copy the "fixed" images that don't go through processing into the images/directory */
copy: {
dev: {
files: [{
expand: true,
src: 'images_src/fixed/*.{gif,jpg,png}',
dest: 'images/'
}]
},
},
});
grunt.loadNpmTasks('grunt-responsive-images');
grunt.loadNpmTasks('grunt-contrib-clean');
grunt.loadNpmTasks('grunt-contrib-copy');
grunt.loadNpmTasks('grunt-mkdir');
grunt.registerTask('default', ['clean', 'mkdir', 'copy', 'responsive_images']);
};
https://unicode-table.com/en/
watch out image compression level and natural width.
should be less pixels.
Total bits = pixel x bit per pixel
body {
margin: 0;
}
img {
float: left;
margin-right: 10px;
width: calc((100% - 20px)/3);
}
img:last-of-type {
margin-right: 0;
}
Vector scales without quality degradation.
$0.naturalWidth 601 $0.naturalWidth 1202
Characters -> Tokens -> Nodes -> DOM
Request page -> GET html -> page head(build DOM, render) -> search result(build DOM, render)
Characters -> Tokens -> Nodes -> CSSOM
hi tag is faster evaluation than div p tag as dom tree.
JavaScript is parser blocking
Async is a utility module which provides straight-forward, powerful functions for working with asynchronous JavaScript. Although originally designed for use with Node.js and installable via npm install –save async, it can also be used directly in the browser.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<canvas id="my_canvas"></canvas>
</body>
<script>
var canvas = null;
var context = null;
setup = function(){
canvas = document.getElementById("my_canvas");
context = canvas.getContext('2d');
canvas.width = 1200;
canvas.height = 720;
};
</script>
</html>
<style tyle="text/css">
.container {
width: 100%;
display: flex;
flex-wrap: wrap;
}
.box {width: 150px;}
</style>
column drop, off canvas, layout shifter, mostly fluid
<link rel="stylesheet" href="styles.css"> <link rel="stylesheet" media="screen and (min-width:500px)" href="over500.css">
media query within a style sheet.
@media screen and (min-width: 500px){
body { color: #F79420; }
}
@media screen and (min-width: 800px){
body { background-color: blue; }
}
frequently used max-width and min-width
@media screen and (max-width: 500px){
.yes {
opacity: 1;
}
. no {
opacity: 0;
}
}
change background-color with width.
body {
background-color: green;
}
@media screen and (max-width: 400px) {
body {
background-color: red;
}
}
@media screen and (min-width: 600px) {
body {
background-color: blue;
}
}
developer tool help you to decide media query
<meta name="viewport" content="width=device-width, initial-scale=1">
initial-scale indicate relationship between device independent pixel and css pixel.
<meta name="viewport" content="width=360,initial-scale=1">
prevent image overflow content
img, embed, object, video {
max-width: 100%
}
example
<img id="owl">
#owl {
width: 640px;
max-width: 100%;
}
CSS/Properties
https://www.w3.org/community/webed/wiki/CSS/Properties
nav a, button {
min-width: 48px;
max-height: 48px;
}