Xiang Wang @ 2018-08-14 09:14:37

NumberFormat 

new Intl.NumberFormat("zh-cn", config).format(10020)

Array 数组, 官网 

Date 

示例代码

new Date();  // 获取当前时间
var time2 = new Date(3000);  // 从标准时间到现在的时间, 但是这个是localhost的
console.log(time2);
var time3 = new Date('2016-09-13T07:55:16.742Z');
console.log(time3);
console.log(time3.toISOString()) "%y-%m-%dT%H:%M:%S.000Z"这种格式

注意事项
- 月份是从0开始计算的，但是日期是从1开始计算的
- Date(2013, 13, 1) 和 Date(2014, 1, 1) 等价。类似的如果秒也是这样，那也等价
Methods
- Date.now() // 1520395758500

Number 

NumberFormat 

new Intl.NumberFormat(
    'en-US',
    {notation: 'compact', maximumSignificantDigits: 4}
).format(123_000_0)  // 1.23M

Object API 

删除一个key

var myobj = new Object;
myobj.a = 5;
myobj.b = 12;
delete myobj.a;

获取keys

Object.keys(obj)

RegExp正则表达式 

regexp guid

创建一个正则表达式

var re = /ab+c/;  // js载入时就编译好了，速度快
var re = new RegExp('ab+c');  // 速度慢，但是里面的内容可变

使用特殊字符
- [ ] \v
- \w: alphanumeric character(包括underscore) [A-Za-z0-9_]
- \W: 和\w相反，匹配所有非数字字母下划线的字符
- [ ] \n
使用括号

var re = /(\d+)(\w+)/
re.exec('123abc')[1] == '123'
re.exec('123abc')[2] == 'abc'

Syntax 语法:

/pattern/flags
new RegExp(pattern[, flags])
RegExp(pattern[, flags])
/ab+c/i;
new RegExp('ab+c', 'i');
new RegExp(/ab+c/, 'i');

Examples 示例

'123fea'.replace(/\d+/, 'd')
# change data format
var re = /(\w+)\s(\w+)/;
var str = 'John Smith';
var newstr = str.replace(re, '$2, $1');
console.log(newstr);
# use regular expression to split lines
var text = 'Some text\nAnd some more\r\nAnd yet\rThis is the end';
var lines = text.split(/\r\n|\r|\n/);
console.log(lines); // logs [ 'Some text', 'And some more', 'And yet', 'This is the end' ]

Set 

const mySet = new Set()
mySet.add(1)
mySet.add(5)
mySet.add(5)
for (let item of set) console.info(set)

String 字符串 

Template literals 模板 

`hello ${who}`
escape `<a>${who}</a>`

indexOf

Syntax

str.indexOf(searchValue)
str.indexOf(searchValue, fromIndex)  // fromIndex代表从哪个位置开始寻找，默认为0

寻找一个字符串内出现了几次某个字母

const str = 'To be, or not to be, that is the question.';
let count = 0;
let position = str.indexOf('e');

while (position !== -1) {
  count++;
  position = str.indexOf('e', position + 1);
}

console.log(count); // displays 4

Split

str.split([separator[, limit]]) * separator
The separator can be string or regular expression, if it is space, no split will happen (different from python) * limit
limit the number of splits to be found. only return the first limit items. (different from python. in python the limit means after limit times split, the rest world will not split and return a a whole world) * return
return an Array or strings * Example var namelist = 'Harry Trump ;Fred Barney; Helen Rigby ; Bill Abel ;Chris Hand '; var re = /\s*;\s*/ var namelist = names.split(re); // If separator is regular expression that contains capturing parentheses (), matched results are included in array 如果正则表达式里面有括号，那么分割的信息也会显示在array里面。注意这个括号要是group的那种，不能是把几个符号合并的那种 var myString = 'Hello 1 word. Sentence number 2.'; // 比较这三者的区别 myString.split(/\s*\d\s*/) ["Hello", "word. Sentence number", "."] myString.split(/(\s*\d\s*)/) ["Hello", " 1 ", "word. Sentence number", " 2", "."] myString.split(/\s*(\d)\s*/) ["Hello", "1", "word. Sentence number", "2", "."]

Symbol 

产生唯一的符号. 不过用在字典里会导致失效, 用变量名替换

Array 数组, 官网

Array 数组, 官网 