Does JavaScript have an indexOf(lambda) or similar?

Question

I want to return the index of the first element satisfying a unary predicate.

Example:

[1,2,3,4,5,6,7].indexOf((x) => x % 3 === 0) // returns 2

Is there such a function? The alternative I was going to use was

[1,2,3,4,5,6,7].reduce((retval,curelem,idx) => 
{
   if(curelem % 3 === 0 && retval === undefined)
       retval = idx; 
   return retval;
}, undefined);

but of course that would be less efficient since it doesn't stop iterating through the array after it has found the element.

Answer 1

Yes, there is such function: Array.prototype.findIndex. The method was introduced by ECMAScript 2015 and you need to use a polyfill for supporting older browsers.