javascript new array foreach 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: what is foreach method in javascript

var arr = [1, 2, 3, 4, 5, 6];

//var sum = 0;
arr.forEach(function (value, index, array){  // Built in method
    //sum += value;
    console.log(value, index, array);
})

//console.log(sum);  // We can print sum of all Array element (if those are numbers)

// function forEach(arr, cb){  // How forEach() method works
//     for (var i = 0; i<arr.length; i++){
//         cb(arr[i], i, arr);
//     }
// }
// var sum = 0;
// forEach(arr, function (value, index, arr){
//     console.log(value, index, arr);
//     sum += value;
// })
// console.log(sum);