Javascript, search for a string using regex in a specific tag and replace it with mathematical value

regexReplaceInPage.js

// This function basically will search for prices per hour in AWS webpage and replace it with Monthly price
function findAndReplace(tag) {
    var content = document.getElementsByTagName(tag)[0].innerHTML; 
	// This pattern will search for strings like `$0.023 per Hour`
    var pattern = /\$\d+\.\d+\sper\sHour/g;
    content = content.replace(pattern, 
		function(entry) { 
	    			// This will extract float value only
				pattern = /\d+\.\d+/g
				return '$'+ 24 * 30 * parseFloat(entry.match(pattern)) + ' per Month'
			}
		);
    document.getElementsByTagName(tag)[0].innerHTML = content;
}

findAndReplace("main"); // will search for all strings matches in <main> tag