/* bad */
img {
display: block;
}
/* good */
img {
vertical-align: middle;
}
同样，尽量不要使元素脱离文本流。
/* bad */
div {
width: 100px;
position: absolute;
right: 0;
}
/* good */
div {
width: 100px;
margin-left: auto;
}
Positioning（定位）
There are many ways to position elements in CSS but try to restrict yourself to the properties/values below. By order of preference: 在CSS有很多方法来定位元素，但是尽可能限制自己的属性/值在下面。按优先顺序:
// bad (albeit way faster)
const arr = [1, 2, 3, 4];
const len = arr.length;
var i = -1;
var result = [];
while (++i < len) {
var n = arr[i];
if (n % 2 > 0) continue;
result.push(n * n);
}
// good
const arr = [1, 2, 3, 4];
const isEven = n => n % 2 == 0;
const square = n => n * n;
const result = arr.filter(isEven).map(square);
Embrace implicit coercion when it makes sense. Avoid it otherwise. Don't cargo-cult.
// bad
if (x === undefined || x === null) { ... }
// good
if (x == undefined) { ... }
Loops
Don't use loops as they force you to use mutable objects. Rely on array.prototype methods. 不要使用循环,如果他们强迫你使用可变的对象。依赖array.prototype方法。
// bad
const sum = arr => {
var sum = 0;
var i = -1;
for (;arr[++i];) {
sum += arr[i];
}
return sum;
};
sum([1, 2, 3]); // => 6
// good
const sum = arr =>
arr.reduce((x, y) => x + y);
sum([1, 2, 3]); // => 6
如果你不能，或者如果使用array.prototype被认为是滥用的，那么使用递归。
// bad
const createDivs = howMany => {
while (howMany--) {
document.body.insertAdjacentHTML("beforeend", "");
}
};
createDivs(5);
// bad
const createDivs = howMany =>
[...Array(howMany)].forEach(() =>
document.body.insertAdjacentHTML("beforeend", "")
);
createDivs(5);
// good
const createDivs = howMany => {
if (!howMany) return;
document.body.insertAdjacentHTML("beforeend", "");
return createDivs(howMany - 1);
};
createDivs(5);
Arguments
忘记 arguments 对象， rest参数是更好地选择，因为:
他的名字更容易让你知道该函数所希望的参数是什么。
这是一个真正的数组, 更容易使用.
// bad
const sortNumbers = () =>
Array.prototype.slice.call(arguments).sort();
// good
const sortNumbers = (...numbers) => numbers.sort();
Apply
忘记 apply(). 使用扩展运算符代替。
const greet = (first, last) => `Hi ${first} ${last}`;
const person = ["John", "Doe"];
// bad
greet.apply(null, person);
// good
greet(...person);
Bind
不要使用bind() 当有更好的方法时.
// bad
["foo", "bar"].forEach(func.bind(this));
// good
["foo", "bar"].forEach(func, this);
// bad
const person = {
first: "John",
last: "Doe",
greet() {
const full = function() {
return `${this.first} ${this.last}`;
}.bind(this);
return `Hello ${full()}`;
}
}
// good
const person = {
first: "John",
last: "Doe",
greet() {
const full = () => `${this.first} ${this.last}`;
return `Hello ${full()}`;
}
}
Higher-order functions（高阶函数）
不要嵌套函数，当非必要时
// bad
[1, 2, 3].map(num => String(num));
// good
[1, 2, 3].map(String);
Composition
Avoid multiple nested function calls. Use composition instead. 避免调用多个嵌套函数。使用组合代替。
const plus1 = a => a + 1;
const mult2 = a => a * 2;
// bad
mult2(plus1(5)); // => 12
// good
const pipeline = (...funcs) => val => funcs.reduce((a, b) => b(a), val);
const addThenMult = pipeline(plus1, mult2);
addThenMult(5); // => 12
// bad
var me = new Map();
me.set("name", "Ben").set("country", "Belgium");
// good
const me = new Map();
me.set("name", "Ben").set("country", "Belgium");
Conditions（条件）
用IIFE's来返回语句好于if, else if, else 和switch 语句.
// bad
var grade;
if (result < 50)
grade = "bad";
else if (result < 90)
grade = "good";
else
grade = "excellent";
// good
const grade = (() => {
if (result < 50)
return "bad";
if (result < 90)
return "good";
return "excellent";
})();
Object iteration
尽可能避免使用for...in 。
const shared = { foo: "foo" };
const obj = Object.create(shared, {
bar: {
value: "bar",
enumerable: true
}
});
// bad
for (var prop in obj) {
if (obj.hasOwnProperty(prop))
console.log(prop);
}
// good
Object.keys(obj).forEach(prop => console.log(prop));
Objects as Maps
当对象合法使用情况下,maps通常是一个更好的,更强大的选择。有困惑时,请使用一个“Map”。
// bad
const me = {
name: "Ben",
age: 30
};
var meSize = Object.keys(me).length;
meSize; // => 2
me.country = "Belgium";
meSize++;
meSize; // => 3
// good
const me = new Map();
me.set("name", "Ben");
me.set("age", 30);
me.size; // => 2
me.set("country", "Belgium");
me.size; // => 3
1. 创建一个maven项目
2. 创建com.CoberturaStart.java
package com;
public class CoberturaStart {
public void helloEveryone(){
System.out.println("=================================================
我并不知道出现这个问题的实际原理,只是通过其他朋友的博客,文章得知的一个解决方案,目前先记录一个解决方法,未来要是真了解以后,还会继续补全.
在mysql5中有一个safe update mode,这个模式让sql操作更加安全,据说要求有where条件,防止全表更新操作.如果必须要进行全表操作,我们可以执行
SET
public class DeleteSpecificChars {
/**
* Q 63 在字符串中删除特定的字符
* 输入两个字符串，从第一字符串中删除第二个字符串中所有的字符。
* 例如，输入”They are students.”和”aeiou”，则删除之后的第一个字符串变成”Thy r stdnts.”
*/
public static voi
File descriptors are represented by the C int type. Not using a special type is often considered odd, but is, historically, the Unix way. Each Linux process has a maximum number of files th
