Question

I just tried this code in Chrome deveoper tools:

var str = "1111111";
str[0] = 2;
2
console.log(str[0]);
1

As you can see, the output was 1, where I expected 2. My conclusion is this is not meant to be working like that, so I ask how would I get this to work – how would I change the first ‘item’ of the varable str to 2?

Answer 1

That is because in JavaScript strings are immutable objects. You should use substr function:

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

var str = '11111';
console.log(str.replaceAt(0, '2'));