How do I replace a character at a particular index in JavaScript?

Question

I have a string, let's say Hello world and I need to replace the char at index 3. How can I replace a char by specifying a index?

var str = "hello world"; 

I need something like

str.replaceAt(0,"h"); 

Answer 1

In JavaScript, strings are immutable, which means the best you can do is to create a new string with the changed content and assign the variable to point to it.

You'll need to define the replaceAt() function yourself:

String.prototype.replaceAt = function(index, replacement) {     return this.substr(0, index) + replacement + this.substr(index + replacement.length); } 

And use it like this:

var hello = "Hello World"; alert(hello.replaceAt(2, "!!")); // He!!o World 

Answer 2

There is no replaceAt function in JavaScript. You can use the following code to replace any character in any string at specified position:

function rep() {     var str = 'Hello World';     str = setCharAt(str,4,'a');     alert(str); }  function setCharAt(str,index,chr) {     if(index > str.length-1) return str;     return str.substring(0,index) + chr + str.substring(index+1); }

<button onclick="rep();">click</button>