what is replace in js code example

Example: javascript string replace

const p = 'Its going to rain today and its going to rain tomorrow';

// Example of replacing all occurrances

// g = global search, which searches all instances
// i = case insensitive, which will match 'a' with 'A'
const regex = /rain/gi;
console.log(p.replace(regex, 'snow'));
// expected output: "Its going to snow today and its going to snow tomorrow"

// Example of replacing the first occurance
console.log(p.replace('rain', 'snow'));
// expected output: "Its going to snow today and its going to rain tomorrow"