How to Perform Multiple String Replacements in JavaScript?

Multiple String Replacement in JavaScript

String replacement is a common task in programming. In JavaScript, the replace() method allows you to replace a single match of a specified string with a new one. However, what if you want to replace multiple strings with multiple other strings at the same time?

Consider the following example:

var str = "I have a cat, a dog, and a goat.";

// Attempt to replace multiple strings with incorrect results
str = str.replace(/cat/gi, "dog");
str = str.replace(/dog/gi, "goat");
str = str.replace(/goat/gi, "cat");

// Output: "I have a cat, a cat, and a cat"

As you can see, this does not produce the desired result of "I have a dog, a goat, and a cat." Instead, it incorrectly substitutes every instance of "cat" with "dog," and so on.

Specific Solution

To achieve the desired result, you can use a function to handle each replacement:

var str = "I have a cat, a dog, and a goat.";
var mapObj = {
   cat:"dog",
   dog:"goat",
   goat:"cat"
};
str = str.replace(/cat|dog|goat/gi, function(matched){
  return mapObj[matched];
});

// Output: "I have a dog, a goat, and a cat"

In this approach, we create a map object (mapObj) that defines the key-value pairs of strings to be replaced. Then, we use a regular expression that matches any of these strings and replaces them with the corresponding value from the map object.

Generalizing the Solution

To generalize this approach, you can dynamically create the regular expression and update the map object as needed:

var mapObj = {cat:"dog",dog:"goat",goat:"cat"};

var re = new RegExp(Object.keys(mapObj).join("|"),"gi"); 
str = str.replace(re, function(matched){
  return mapObj[matched];
});

This approach allows you to add or remove replacement pairs without modifying the regular expression itself.

Reusable Function

To further abstract the process, you can create a reusable function:

function replaceAll(str,mapObj){
    var re = new RegExp(Object.keys(mapObj).join("|"),"gi");

    return str.replace(re, function(matched){
        return mapObj[matched.toLowerCase()];
    });
}

You can then use this function to replace multiple strings with multiple other strings in any given string.

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