1.trim用法
var num = " 2132132114 "
var sum = num.trim()
console.log(sum)
2.indexof用法
var str = "440902200002272430"
var str2 = str.indexOf('20')
console.log(str2)
3.lastIndexof用法
var str = "440902200002272430"
var str2 = str.lastIndexOf('24')
console.log(str2)