How can I perform a str_replace in JavaScript, replacing text in JavaScript?

Question

You would use the replace method:

text = text.replace('old', 'new');

The first argument is what you're looking for, obviously. It can also accept regular expressions.

Just remember that it does not change the original string. It only returns the new value.

More simply:

city_name=city_name.replace(/ /gi,'_');

Replaces all spaces with '_'!

All these methods don't modify original value, returns new strings.

var city_name = 'Some text with spaces';

Replaces 1st space with _

city_name.replace(' ', '_'); // Returns: "Some_text with spaces" (replaced only 1st match)

Replaces all spaces with _ using regex. If you need to use regex, then i recommend testing it with https://regex101.com/

city_name.replace(/ /gi,'_');  // Returns: Some_text_with_spaces 

Replaces all spaces with _ without regex. Functional way.

city_name.split(' ').join('_');  // Returns: Some_text_with_spaces

You should write something like that :

var text = "this is some sample text that i want to replace";
var new_text = text.replace("want", "dont want");
document.write(new_text);

The code that others are giving you only replace one occurrence, while using regular expressions replaces them all (like @sorgit said). To replace all the "want" with "not want", us this code:

var text = "this is some sample text that i want to replace";
var new_text = text.replace(/want/g, "dont want");
document.write(new_text);

The variable "new_text" will result in being "this is some sample text that i dont want to replace".

To get a quick guide to regular expressions, go here:
http://www.cheatography.com/davechild/cheat-sheets/regular-expressions/
To learn more about str.replace(), go here:
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/replace
Good luck!