better way to replace string with various scenarios in javascript

Question

How to replace special characters for different pattern of same string in javascript

am passing one string at a time and below are string patterns

var str1="2456 #02-567"
var result = str1.replace(/#/g, '')

var str1="2-567 2456"
var result = str1.replace(/^/g, '0')

for these strings

2456 #02-567 , 2456 02-567, 2456 2-567,2456 #2-567

Expected Output 
2456 02-567 
 ===========
for these strings
#02-567 2456 , 2-567 2456, 02-567 2456, #2-567 2456

Expected Output 
02-567 2456

Answer 1

May be there is a clever solution, but this should work:

 let str = ["2456 #02-567", "2456 02-567", "2456 2-567","2456 #2-567","#02-567 2456", "2-567 2456", "02-567 2456", "#2-567 2456","1234 12-345","1234 #12-345","#12-345 1234"]; //1234 12-345" or "1234 #12-345" or "#12-345 1234" for(let st of str) console.log(st.replace(/#?(\d)?(\d-)/g,replacer)) function replacer(match, p1, p2, offset, string){ let replaceSubString = p1 || "0"; replaceSubString += p2; return replaceSubString; }

I'm using a captouring group (expression in the parenthesis in the regular expression) that can be referenced in the second parameter of replace function with $1 (1 because is the first captouring group). The ? instead point that the character is optional.