what is indexof in javascript

                                    //indexOf getting 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

                                    const paragraph = 'The quick brown fox';

console.log(paragraph.indexOf('T'));
>> 0

console.log(paragraph.indexOf('h'));
>> 1

console.log(paragraph.indexOf('Th'));
>> 0

console.log(paragraph.indexOf('he'));
>> 1

console.log(paragraph.indexOf('x'));
>> 18

                                    
var str = "Please locate where 'locate' occurs!";

var ind1 = str.indexOf("locate"); // return location of first value which founded
var ind2 = str.lastIndexOf("locate"); // return location of last value which founded
var ind3 = str.indexOf("locate", 15); // start search from location 15 and then take first value which founded
var ind4 = str.search("locate");
//The search() method cannot take a second start position argument. 
//The indexOf() method cannot take powerful search values (regular expressions).

document.write("<br>" + "Length of string:", len);
document.write("<br>" + "indexOf:", ind1);
document.write("<br>" + "index of last:", ind2);
document.write("<br>" + "indexOf with start point:", ind3);
document.write("<br>" + "search:", ind4);

                                    //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}
/>

                                    how to use index