What does indexOf() do in JavaScript?

The indexOf () method compares searchElement to elements of the array using strict equality (the same algorithm used by the === operator). NaN values are never compared as equal, so indexOf () always returns -1 when searchElement is NaN. The indexOf () method skips empty slots in sparse arrays. The indexOf () method is generic.

What is indexOf() method?

The indexOf () method is generic. It only expects the this value to have a length property and integer-keyed properties. The following example uses indexOf () to locate values in an array. You cannot use indexOf () to search for NaN.

What is an index JS file?

An index.js file allow you to import (or require ()) its parent folder as a module. This behavior is copied from Node.js, which has covers this in its documentation under Folders as Modules – "If there is no package.json file present in the directory, then Node.js will attempt to load an index.js or index.node file out of that directory."

How to find the index of a string in JavaScript?

The str.indexOf () function finds the index of the first occurrence of the argument string in the given string. The value returned is 0-based. Also, it returns -1 if the value to search for never occurs. The first argument, searchValue is the string that is to be searched in the base string.