perform a function on each element of array javascript

1/** 1. Use forEach and related */
2var a = ["a", "b", "c"];
3a.forEach(function(entry) {
4    console.log(entry);
5});
6
7/** 2. Use a simple for loop */
8var index;
9var a = ["a", "b", "c"];
10for (index = 0; index < a.length; ++index) {
11    console.log(a[index]);
12}
13
14/**3. Use for-in correctly*/
15// `a` is a sparse array
16var key;
17var a = [];
18a[0] = "a";
19a[10] = "b";
20a[10000] = "c";
21for (key in a) {
22    if (a.hasOwnProperty(key)  &&        // These checks are
23        /^0$|^[1-9]\d*$/.test(key) &&    // explained
24        key <= 4294967294                // below
25        ) {
26        console.log(a[key]);
27    }
28}
29
30/** 4. Use for-of (use an iterator implicitly) (ES2015+) */
31const a = ["a", "b", "c"];
32for (const val of a) {
33    console.log(val);
34}
35
36/** 5. Use an iterator explicitly (ES2015+) */
37const a = ["a", "b", "c"];
38const it = a.values();
39let entry;
40while (!(entry = it.next()).done) {
41    console.log(entry.value);
42}
43

1var new_array = old_array.map(function(e) { 
2  e.data = e.data.split(','); 
3  return e;
4});

1var fruits = ["apple", "orange", "cherry"];
2fruits.forEach(myFunction);
3
4function myFunction(item, index) {
5  document.getElementById("demo").innerHTML += index + ":" + item + "<br>";
6}