Learning JavaScript Data Structures and Algorithms - Third Edition

Searching

We have two search options: the indexOf method, which returns the index of the first element that matches the argument passed, and lastIndexOf, which returns the index of the last element found that matches the argument passed. Let's go back to the numbers array that we were using before:

console.log(numbers.indexOf(10));  
console.log(numbers.indexOf(100)); 

In the previous example, the output in the console would be 9 for the first line and -1 (because it does not exist in our array) for the second line. We can get the same result with the following code:

numbers.push(10);  
console.log(numbers.lastIndexOf(10)); 
console.log(numbers.lastIndexOf(100)); 

We added a new element with the value 10, so the second line will output 15 (our ...