findIndex

Function

Objectives

  • Describe and use the findIndex function

  • Implement the findIndex on your own

function findIndex(array, callback) {
  // findIndex code to be implemented
}

findIndex Definition

function callback(curElement, curIndex, array) {
  // callback implemented by caller of function
}

Returns the index of the first element in the array for which the callback returns a truthy value.  -1 is returned if the callback never returns a truthy value.

var arr = [3,4,6,2,1];
findIndex(arr, function(num, index, array) {
  return num === 6;
});

findIndex Example: Find A Number

Returned Result:

2

var arr = [5,11,13,8,6,7];
findIndex(arr, function(num, index, array) {
  return num % 2 === 0;
});

findIndex Example: Find First Even

Returned Result:

3

var langs = ["Java", "C++", "Python", "Ruby"];
findIndex(langs, function(lang, index, arr) {
  return lang === "JavaScript";
});

findIndex Example: Could Not Find

Returned Result:

-1

var langs = ["Java", "C++", "JavaScript"];
findIndex(langs, function(lang, index, arr) {
  lang === "JavaScript";
});

findIndex Example: Bad Callback

Returned Result:

-1

YOUR

TURN