js array for each code example

Example 1: For-each over an array in JavaScript

/** 1. Use forEach and related */
var a = ["a", "b", "c"];
a.forEach(function(entry) {
    console.log(entry);
});

/** 2. Use a simple for loop */
var index;
var a = ["a", "b", "c"];
for (index = 0; index < a.length; ++index) {
    console.log(a[index]);
}

/**3. Use for-in correctly*/
// `a` is a sparse array
var key;
var a = [];
a[0] = "a";
a[10] = "b";
a[10000] = "c";
for (key in a) {
    if (a.hasOwnProperty(key)  &&        // These checks are
        /^0$|^[1-9]\d*$/.test(key) &&    // explained
        key <= 4294967294                // below
        ) {
        console.log(a[key]);
    }
}

/** 4. Use for-of (use an iterator implicitly) (ES2015+) */
const a = ["a", "b", "c"];
for (const val of a) {
    console.log(val);
}

/** 5. Use an iterator explicitly (ES2015+) */
const a = ["a", "b", "c"];
const it = a.values();
let entry;
while (!(entry = it.next()).done) {
    console.log(entry.value);
}

Example 2: js for each item in array

const array1 = ['a', 'b', 'c'];

array1.forEach(element => console.log(element));

// expected output: "a"
// expected output: "b"
// expected output: "c"

Example 3: for each javascript

let numbers = ['one', 'two', 'three', 'four'];

numbers.forEach((num) => {
  console.log(num);
});  // one   //two //three // four

Example 4: array.foreach

const arr = [0, 3, "hola", "hello", ";", true, [3, 6, 1]];
arr.forEach((element, index) => {
    console.log(element, index);
});

//output:

// 0 0
// 3 1
// hola 2
// hello 3
// ; 4
// true 5
// [3, 6, 1] 6

Example 5: for each array javascript

var fruits = ["apple", "orange", "cherry"];
fruits.forEach(getArrayValues);

function getArrayValues(item, index) {
  console.log( index + ":" + item);
}
/*
result:
0:apple
1:orange
2:cherry
*/

Example 6: forEach

const arraySparse = [1,3,,7]
let numCallbackRuns = 0

arraySparse.forEach((element) => {
  console.log(element)
  numCallbackRuns++
})

console.log("numCallbackRuns: ", numCallbackRuns)

// 1
// 3
// 7
// numCallbackRuns: 3
// comment: as you can see the missing value between 3 and 7 didn't invoke callback function.