npm install array-findindex``javascript
var findIndex = require('array-findindex');
var array = ['a', 'b', 'c', 'd'];
findIndex(array, function (element, index, arr) {
return element === 'c';
});
// => 2
findIndex(array, function (element, index, arr) {
return element === 'z';
});
// => -1
`
Optionally pass in an object as third argument to use as this when executing callback.
`bash``
$ npm install array-findindex