javascript return in foreach code example

Example 1: for each js

const fruits = ['mango', 'papaya', 'pineapple', 'apple'];

// Iterate over fruits below

// Normal way
fruits.forEach(function(fruit){
  console.log('I want to eat a ' + fruit)
});

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: javascript forEach return

const list = [{ name: "John", age: 36 },{ name: "Jack", age: 17 }];

// if you just have to FIND an object with a specific value,
// use Array.prototype.find:
const foundHim = list.find( person => person.name === "John" );
console.log( foundHim );

// if you still want to / need to RETURN the object / value
let returnedHim;
list.forEach( person => {
  if ( person.age === 17 ) {
    returnedHim = person;
  }
});

console.log( returnedHim )

Example 4: what foreach method returns in javascript

function double(arr) {
  return arr.forEach(num => num*2);
}

console.log(double([1,2,3,4])) //undefined