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let text = "Hello world, welcome to the universe.";
/* |-> 1 |-> 14 */
console.log(text.indexOf("el")) // 1
console.log(text.indexOf("el", 3)) // 14
console.log(text.indexOf("69")) // -1
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'a nice string'.indexOf('nice') !== -1 //true
'a nice string'.indexOf('nice', 3) !== -1 //false
'a nice string'.indexOf('nice', 2) !== -1 //true