javascript - Struggling to Understand the Parameter Content when using .map on Function Expressions -


so i'm looking @ function expressions.

this code i'm playing with:

var modifiednames = [ "thomas meeks",                       "gregg pollack",                       "christine wong",                       "dan mcgaw" ];  modifiednames.map(function(cheese) {   alert("yo, " + cheese + "!"); });

it works fine i'm having trouble understanding part of it. grasp .map doing parameter throwing me. how parameter collecting array's information? called cheese that's go-to test word.

i have read couple of explanations i'm not grasping it, hoping here simplify explanation somewhat. thank you.

you're passing function .map(), runs loop, , invokes function on every iteration, passing current item.

think of this:

for (var = 0; < array.length; i++) {   callback(array[i]); }

here array array on called .map(), , callback function passed in.

this isn't mysterious now. it's calling function in loop.

of course, .map() more work , passes more args, shows how parameter gets populated.

a more complete implementation of map this:

array.prototype.mymap = function(callback, thisarg) {   var result = new array(this.length);    (var = 0; < this.length; i++) {     if (i in this) {       result[i] = callback.call(thisarg, this[i], i, this);     }   }   return result; };

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