JS replace not working on string

Question

Trying to replace all instances of # in a string with a variable. It's not working but not retuning any error either.

answer_form = '<textarea name="answer_#" rows="5"></textarea>'+
              '<input type="file" name="img_#" />';

question_num = 5;

answer_form.replace(/#/g, question_num);

The hashes remain.

Not sure what I'm missing?

jfriend00 · Accepted Answer · 2012-09-01T21:53:41.487

184

.replace() returns a new string (it does not modify the existing string) so you would need:

answer_form = answer_form.replace(/#/g, question_num);

You probably should also make question_num a string though auto type conversions probably handle that for you.

Working example: http://jsfiddle.net/jfriend00/4cAz5/

FYI, in Javascript, strings are immutable - an existing string is never modified. So any method which makes a modification to the string (like concat, replace, slice, substr, substring, toLowerCase, toUpperCase, etc...) ALWAYS returns a new string.

edited Sep 01 '12 at 21:53

answered Sep 01 '12 at 21:42

jfriend00

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`.splice()` is an exception. It modifies the string, as well as returns the substring. – Shubham Kushwah Nov 05 '19 at 10:17
2

@ShubhamKushwah - I think you're confused here. There is no `.splice()` method for strings (it is available for arrays). – jfriend00 Nov 05 '19 at 16:34
You're right @jfriend00 - I was in the mindset that if `.slice()` is there, then `.splice()` would be too. Glad to know. – Shubham Kushwah Nov 06 '19 at 18:37

score 10 · Answer 2 · answered Sep 01 '12 at 21:44

Your code is correct. Just add the value to the variable like this:

answer_form = '<textarea name="answer_#" rows="5"></textarea>'+
              '<input type="file" name="img_#" />';

question_num = 5;

answer_form = answer_form.replace(/#/g, question_num);

JS replace not working on string

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