Regular expression: judge whether it conforms to USD format

Title Description ：

Operation steps  

The topic uses regular expressions to determine the string format , My other two previous articles   Thousand digit separated number ,  Regular expressions

function isUSD(str) {
    var reg = /^\$\d{1,3}(,\d{3})*(\.\d{2})?$/
    return reg.test(str)
}

  You can see that the code using regular expressions is so simple and efficient , Learning regular expressions well does provide a lot of convenience in daily work and study .

/^\$\d{1,3}(,\d{3})*(\.\d{2})?$/

^ First line match                \ $    Ahead \ It's the escape character , Represents a match Dollar symbol $

\d{1-3}  Express   matching 1 to 3 A digital   

（） Is the grouping consistent with      (,\d{3})*  Express Comma followed by 3 Any number , * Represents a match 0 Or many times

(\.\d{2})?      \. It means escaping the decimal point   , The entire statement represents   Decimal point followed by 2 Any number ,？ Represents a match 0 or 1 Time                          

$ Indicates that the end of the line matches