js contains code example

Example 1: if str contains jquery

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

Example 2: check for substring javascript

const string = "javascript";
const substring = "script";

console.log(string.includes(substring));  //true

Example 3: check if word is in string javascript

var str = "Hello world, welcome to the universe.";
var n = str.includes("world");

Example 4: javascript string contains

var string = "foo",
    substring = "oo";

console.log(string.includes(substring));

Example 5: 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 6: javascript string contains function

s = "Hello world";
console.log(s.includes("world"));