A constant variable defined with the primitive types like number, string cannot be changed. But I tried the following example in console and got unexpected behaviour.

const word = "example";
word[0] = 'a';
console.log(word) //prints "example"
console.log(word[0]) // prints "e"

As word variable is declared with the const and as the string is a primitive data type and as per the rule, we cannot change the constant string than how come the 2nd line in above code did not gave any error?