How do I swap substrings within a string?

Question

I am trying to swap all occurrences of a pair of substrings within a given string.

For example, I may want to replace all occurrences of \"coffee\" with \"tea\" and

Answer 1

What about

theString.replace(/(coffee|tea)/g, function($1) {
     return $1 === 'coffee' ? 'tea' : 'coffee';
});

(Personally I think it's a crime to swap coffee and tea, but that's your business)

Answer 2

Use a map (an object) to define what replaces what and then a function to tap into the map:

D:\MiLu\Dev\JavaScript :: type replace.js
function echo(s) { WScript.Echo(s) }
var
map = { coffee: "tea", tea: "coffee" },
str = "black tea, green tea, ice tea, teasing peas and coffee beans";
echo( str.replace( /\b(tea|coffee)\b/g, function (s) { return map[s] } ) );

D:\MiLu\Dev\JavaScript :: cscript replace.js
black coffee, green coffee, ice coffee, teasing peas and tea beans

Answer 3

Based on @alexander-gessler's answer, but with support for dynamic inputs.

(While potentially opening the door to code injection.)

function swapSubstrings(string, a, b) {
  return string.replace(
    new RegExp(`(${a}|${b})`, "g"),
    match => match === a ? b : a
  )
}

Answer 4

Close. Consider this:

var newString = oldString.replace("tea|coffee", function(match) {
    // now return the right one, just a simple conditional will do :)
});

Happy coding.

Answer 5

You can use a function:

var str = "I like coffee more than I like tea";
var newStr = str.replace(/(coffee|tea)/g, function(x) {
   return x === "coffee" ? "tea" : "coffee";
});
alert(newStr); 

Running example