arrays - what use does the javascript forEach method have (that map can't do)? -

The only difference between map and foreground is that the map is returning an array and forEach method " func.call (scope, this [i], i, this) for not for everyone; ". For example, " this " and " radius " are not references to the same object and it [i] and are not Referring to the existing value in the loop?

I said on another post that "Use based on each code for example, you can add things to the page, for example. Basically, when you want "side effects" it is very good. I do not know what the side effects mean.

  array.prototype.map = function (FNC) {var A = new array (this.length); for (var i = 0; i & lt; this.length; i ++) {a [i] = fnc (this [i];};) a;) array .prototype P.fireh = function (funk, scope) {scope = scope} for it (var i = 0, l = this.length; i & lt; l; i ++) {happy at end, in JavaScript There are no real uses for methods (since we are not updating a database). Call (this, except the manip, such ulate number:  
  alert ([1,2, 3,4] .map (function (x) {return x + 1}); // This is the only example, I never see the map in JavaScript.  
 
 Any answer Thanks. 
 map  and  in your example  
 
 
  ForEach  is running on the original array elements, while  map  clearly gives a new array. 
 
 With  for  you are taking some action - and alternatively changing - each element in the original array For the  forEach  method, you run the function provided for each element, but anything returns ( undefined ). On the other hand, the  map runs through the array, applying a function to each element, and  removes the result as a new array   < For p <  with "side effect" the original array is changing. There is no "side effect" with  map , in idiomatic usage, the original array element  not  is changed; Each element has a one-by-one mapping in the original array - the mapping transfold is of your provided function. 
 
 The fact is that there is no database involved in it does not mean that you will not work on data structures, which is one of the essence of programming in any language after all. . For your last question, your orange can contain numbers, but not objects, strings, functions etc.