Replace '-' with '--' in a JavaScript string

Question

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,'--')

score 16 · Accepted Answer · edited Jan 17 '16 at 07:14

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

Not only in JavaScript but nearly in all major languages string variables are immutable. — Kamran Shahid, Jan 17 '16 at 07:06

score 7 · Answer 2 · answered Jan 17 '16 at 06:59

7

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,'--')

answered Jan 17 '16 at 06:59

techfoobar

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score 4 · Answer 3 · answered Jan 17 '16 at 06:58

4

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

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

answered Jan 17 '16 at 06:58

whatoncewaslost

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As explained in other answers, this should work only when the character you're splitting by is same as used in the string. – Tushar Jan 17 '16 at 07:16

Replace '-' with '--' in a JavaScript string

3 Answers3