js string not contains code example

Example 1: javascript contains substring

var str = "We got a poop cleanup on isle 4.";
if(str.indexOf("poop") !== -1){
	alert("Not again");
}
//use indexOf (it returns position of substring or -1 if not found)

Example 2: js string does not contain

"this is the string".indexOf("cake"); // -1 (does not contain)
"this string has cake".indexOf("cake"); // 16 (contains)