How can I write a replace method for String in JavaScript?

Question

I heard, that string in JavaScript has immutability.

So, how can I write a method to replace some character in string?

What I want is:

String.prototype.replaceChar(char1, char2) {
    for (var i = 0; i < this.length; i++) {
        if (this[i] == char1) {
            this[i] = char2;
        }
    }
    return this;
}

Then, I can use it like this:

'abc'.replaceChar('a','b'); // bbc

I know it will not work, because the immutability of string.

But in native code, I can use the native replace method like this:

'abc'.replace(/a/g,'b');

I don't really know how to solve this problem.

Answer 1

You can use the following approach:

String.prototype.replaceAll = function(search, replacement) {
    return this.replace(new RegExp(search, 'g'), replacement);
};

Answer 2

If you want a solution without regex (as a way to learn), you can use the following:

 String.prototype.replaceChar = function(char1, char2) { var s = this.toString(); for (var i = 0; i < s.length; i++) { if (s[i] == char1) { s = s.slice(0, i) + char2 + s.slice(i+1); } } return s; } console.log('aaabaaa'.replaceChar('a', 'c')) 

The idea is that you need this content of the string in a temp variable, then you need to go char-by-char, and if that char is the one you are looking for - you need to build your string again.

Answer 3

You can use array, too:

 String.prototype.replaceChar = function (char1, char2) { newstr=[]; for (i = 0; i < this.length; i++) { newstr.push(this[i]); if (newstr[i] == char1) { newstr[i] = char2 } } return newstr.join(""); } console.log('abca'.replaceChar('a','G'));