match pattern in RegEx in js

Question

I want to edit a pattern that checks if text starts with number/s and ends with number/s or operator and return true or false based on test() method.

How can I do that with JavaScript ?`

var str= "123+125",str2 = "123",str3 = "123*";
let RegularExpression = /^\d*(\d*|(\+|\-|\*|\/){1,})$/; //this pattern variable what I want to edit because it doesn't do what I want. 
let result1 = RegularExpression.test(str);
let result2 = RegularExpression.test(str);
let result2 = RegularExpression.test(str);

Answer 1

You could use repeat 1 or more times matching 1 or more digits, optionally followed by an operator.

^(?:\d+[+*/-]?)+

Explanation

• ^ Start of string
• (?: Non capture group
  • \d+[+*/-]? Match 1+ digits optionally followed by either + * / -
• )+ Close non capture group and repeat 1+ times

Regex demo

 let pattern = /^(?:\d+[+*/-]?)+$/m; [ "123+125", "", "123", "123*", "123+125-1" ].forEach(s => console.log(s + " --> " + pattern.test(s)));

Answer 2

Try this pattern /^(\d*|[+/*-]?){1,}$/

 var str= "123+125",str2 = "123",str3 = "123*"; let RegularExpression = /^(\d*|[+/*-]?){1,}$/; //this pattern variable what I want to edit because it doesn't do what I want. let result1 = RegularExpression.test(str); let result2 = RegularExpression.test(str); let result3 = RegularExpression.test(str); console.log("res1:",result1,",res3:",result2,",res3:",result3)

Answer 3

Use

/^\d+([-+*\/]\d+)*[-+*\/]?$/

See proof

EXPLANATION:

NODE                     EXPLANATION
--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  \d+                      digits (0-9) (1 or more times (matching
                           the most amount possible))
--------------------------------------------------------------------------------
  (                        group and capture to \1 (0 or more times
                           (matching the most amount possible)):
--------------------------------------------------------------------------------
    [-+*\/]                  any character of: '-', '+', '*', '\/'
--------------------------------------------------------------------------------
    \d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
--------------------------------------------------------------------------------
  )*                       end of \1 (NOTE: because you are using a
                           quantifier on this capture, only the LAST
                           repetition of the captured pattern will be
                           stored in \1)
--------------------------------------------------------------------------------
  [-+*\/]?                 any character of: '-', '+', '*', '\/'
                           (optional (matching the most amount
                           possible))
--------------------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string

JavaScript:

 var str= "123+125",str2 = "123",str3 = "123*"; let RegularExpression = /^\d+([-+*\/]\d+)*[-+*\/]?$/; console.log( RegularExpression.test(str) ); console.log( RegularExpression.test(str2) ); console.log( RegularExpression.test(str3) );