Javascript Array concatMap(callback)

Array.prototype.concatMap = function (callback) {
  const newArray = [];//from w ww .j  ava2 s.  c om

  this.map(callback).forEach((element) => {
    element.forEach((element) => {
      newArray.push(element);
    });
  });

  return newArray;
};

'use strict';/* w w w  .ja  va  2  s  .  c o  m*/

Array.prototype.concatMap = function (cb) {
    return this.map(cb).concatAll()
}

/**//from  w w  w  .  java2s  . c o m
 * Function does the same behavior as map and concatAll in action.
 * @param fn => fn is a callback.
 */
Array.prototype.concatMap = function(fn) {
    return this
        .map((item, index, arr) => fn(index))
        .concatAll();
};

Array.prototype.concatMap = function(projectionFunction) {
 return this.map(function(item) {
  return projectionFunction(item);
 })./*from  ww  w.jav  a  2  s. c  om*/
 concatAll();
};

Array.prototype.map = function(callback) {
 var result = [];
 this.forEach(function(item) {
  result.push(callback(item));
 });

 return result;
};

//concatAll() only works on singly nested arrays
//for example: [["a", ["test"]]] returns ["a", >Array[1]]
Array.prototype.concatAll = function(array) {
 var results = [];
 this.forEach(function(subArray) {
    if (Array.isArray(subArray)) {
      subArray.forEach(function(item) {
       results.push(item);
      });
    } else {
     results.push(item);
    }
 });

 return results;
};

var test = [["Build"], ["a"], ["bird's"], ["nest"], ["to"], ["make", "a"], ["test"]];
test.concatMap(function(item) {
 return item;
});