change aparticualr word from string javascript code example

Example 1: replace all occurrences of a string in javascript

const p = 'dog dog cat rat';

const regex = /dog/gi;

console.log(p.replace(regex, 'cow'));
//if pattern is regular expression all matches will be replaced
//output: "cow cow cat rat"

Example 2: how to replace all the string in javascript when the string is javascript variable

function name(str,replaceWhat,replaceTo){
    var re = new RegExp(replaceWhat, 'g');
    return str.replace(re,replaceTo);
}