forEach

The .forEach() method executes a provided function once for each array element.

Syntax:

someArray.forEach(function(element[, index, array]) {

})

Check out the docs.

Example

const friends = ["bob", "alice", "tim", "june"];

// using the old for loop
for (let i = 0; i < friends.length; i++) {
  console.log("Hello, " + friends[i] + "!");
}

// using .forEach()
friends.forEach(function (buddy) {
  console.log("Hi " + buddy + "!");
});

// both output the same thing
// > Hi bob!
// > Hi alice!
// > Hi tim!
// > Hi june!

Note

The callback function (someCallback()) can either be an anonymous or named function (like all callbacks).
This function can receive 3 positional parameters: element, index, container. The position matters, so the first variable name that you pass into this callback will always refer to element, no matter what you call it.
You can omit parameters from the parameter list if you are not using them

[1,2,3].forEach(function(element, index, container) { 
  console.log("----")
  console.log("element value : " + element)
  console.log("index number  : " + index)
  console.log("container     : " + container)
})
// [ 1, 2, 3 ]
// [ 1, 2, 3 ]
// [ 1, 2, 3 ]

.forEach() is just like .map(), except .forEach() always returns undefined

[1,2,3].forEach(function(element) {
  return element
}); // returns undefined

[1,2,3].map(function(element) { return element * 2 }); // returns [2, 4, 6]