Replace '-' with '--' in a JavaScript string [duplicate]

Question

This question already has answers here:

Replace method doesn't work (4 answers)

Closed 7 years ago.

I am trying to replace a single dash '-' character in a string with double dashes.

2015–09–01T16:00:00.000Z
to be
2015-–09-–01T16:00:00.000Z

This is the code I am using but it doesn't seem to be working:

var temp = '2015–09–01T16:00:00.000Z'
temp.replace(/-/g,'--')

Answer 1

In JavaScript Strings are immutable. So, when you modify a string, a new string object will be created with the modification.

In your case, the replace has replaced the characters but returns a new string. You need to store that in a variable to use it.

For example,

var temp = '2015–09–01T16:00:00.000Z';
temp = temp.replace(/–/g,'--');

---

Note The string which you have shown in the question, when copied, I realised that it is a different character but looks similar to – and it is not the same as hyphen (-). The character codes for those characters are as follows

console.log('–'.charCodeAt(0));
// 8211: en dash
console.log('-'.charCodeAt(0));
// 45: hyphen

• Kamran Shahid: Not only in JavaScript but nearly in all major languages string variables are immutable.

Answer 2

The hyphen character – you have in the string is different from the one you have in the RegExp -. Even though they look alike, they are different characters.

The correct RegExp in this case is temp.replace(/–/g,'--')

Answer 3

Probably the easiest thing would be to just use split and join.

var temp = '2015–09–01T16:00:00.000Z'.split("-").join("--");

• Tushar: As explained in other answers, this should work only when the character you're splitting by is same as used in the string.