find a letter in a string javascript code example

Example 1: how to identify specific letter from a string in javascript

var str = "Hello world, welcome to the universe.";
var n = str.includes("world", 12);

Example 2: indexof javascript

//indexOf - JS method to get index of array element. 
// Returns -1 if not found

var colors=["red","green","blue"];
var pos=colors.indexOf("blue");//2

//indexOf getting index of sub string, returns -1 if not found

var str = "We got a poop cleanup on isle 4.";
var strPos = str.indexOf("poop");//9

//Eg with material ui

<Checkbox
   checked={value.indexOf(option) > -1}
   value={option}
/>

Example 3: indexof javascript

Array.indexOf(searchElement, fromIndex)