Useful Functions

Map function

will duplicate an array to another
This will retrieve the ages of everyone 18 or over and add them to the array full

var ages[12, 13, 16, 21]
var full = ages.map(function(curr){
return cur >=18;
})

This will get the 'true' boolean value of ages>= 18 then we have to use the indexOf to find the element position

console.log(ages[full.indexOf(true)]);

ES6 Equivalent This returns the index

var index = ages.findIndex(cur => cur >= 18);

This returns the actual age

var ageover18 = ages.find(cur => 18);

Used to split text given a delimiter into an array of substrings

var myText = 'hello-1'
var mysplit = myText.split('-')

Will Yield

['hello', 1]