how to replace substring in javascript code example

Example 1: javascript replace string

var str = "JavaScript replace method test";
var res = str.replace("test", "success");  
//res = Javscript replace method success

Example 2: how to use the replace method in javascript

let string = 'soandso, my name is soandso';

let replaced = string.replace(/soandso/gi, 'Dylan');

console.log(replaced); //Dylan, my name is Dylan