array for each in javascript code example

Example 1: javascript foreach

const avengers = ['thor', 'captain america', 'hulk'];
avengers.forEach((item, index)=>{
	console.log(index, item)
})

Example 2: 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 3: 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 4: javascript .foreach

let colors = ['red', 'blue', 'green'];
// idx and sourceArr optional; sourceArr == colors
colors.forEach(function(color, idx, sourceArr) {
	console.log(color, idx, sourceArr)
});
// Output:
// red 0 ['red', 'blue', 'green']
// blue 1 ['red', 'blue', 'green']
// green 2 ['red', 'blue', 'green']

Example 5: JavaScript Array Methods .forEach()

let days = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday'];
days.forEach(function log(day) {
  console.log(day)
})

// ES6 verzió óta lehetséges az ún. "array function" használata
// az eredmény ugyanaz lesz, mint az előző szintaxissal
days.forEach(day => {
  console.log(day)
});

// amikor a függvénytörzs egy sor, kapcsos zárójel és sortörés nélkül is
// írhatjuk a függvényt
days.forEach(day => console.log(day));