how to check if substring in string javascript code example

Example 1: if str contains jquery

if (str.indexOf("Yes") >= 0)
  
  //case insensitive version
  if (str.toLowerCase().indexOf("yes") >= 0)

Example 2: javascript check if character exists in string

// With ES6 MDN docs .includes()
"FooBar".includes("oo"); // true
"FooBar".includes("foo"); // false
"FooBar".includes("oo", 2); // false (2 is the start position for the search)

// E: Not suported by IE - instead you can use the Tilde opperator ~ (Bitwise NOT) with .indexOf()
~"FooBar".indexOf("oo"); // -2
~"FooBar".indexOf("foo"); // 0
~"FooBar".indexOf("oo", 2); // 0 (parameter 2 is the start position for the search)

// Used with a number, the Tilde operator effective does ~N => -(N+1). Use it with double negation !! (Logical NOT) to convert the numbers in bools:
!!~"FooBar".indexOf("oo"); // true
!!~"FooBar".indexOf("foo"); // false
!!~"FooBar".indexOf("oo", 2); // false

Example 3: 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 4: string.contains javascript

var str = "We got a poop cleanup on isle 4.";
if(str.indexOf("poop") !== -1){
	alert("Not again");
}

Example 5: js string does not contain

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