字符串截取

let str = ‘2018-08-30’
//截取年
str.substr(0,4) or str.substring(4,0)
=>'2018'
//截取月
str.match(/-(\S*)-/)[1]
=>'08'
//截取日
str.substr(-2)
=>'30'
//手机号中间部分改为*号
var lphone = phone.replace(/^(\d{4})\d{4}(\d+)/,"$1****$2");

//截取自定两字符中间部分

》a
=="2018-08-01 09:38:34"
》a.indexOf('-')
==4
》a.lastIndexOf(':')
==16
》a.slice(a.indexOf('-')+1,a.lastIndexOf(':'))
=="08-01 09:38"

//加个点

art
"123456"
art.substring(0, art.length - 2) + '.' + art.substr(-2)
"1234.56"