var str = "Please locate where 'locate' occurs!";

str.replace("locate", "W3Schools"); //replace only replace first match from string
str.replace(/LOCATE/i, "W3Schools"); // i makes it case insensitive
str.replace(/LOCATE/g, "W3Schools"); // g replace all matches from string rather than replacing only first

document.write("
" + "replace:", res7);
document.write("
" + "replace with case insensitive:", res8);
document.write("
" + "replace all:", res9);