How can i search a specific keyword in webpage

Question

On selecting a and submitting. In background specified keyword should be searched on specific webpage and display success or failure. Can someone help me out with this

Answer 1

// Use

var html = document.querySelector("html");
var txt = html.innerText;

// to get the text of the whole webpage.

// then use

var search = txt.indexOf(searchStr);
if(search != -1) alert(searchStr + " is found");

// to check keywords in the page.