{"id":1727,"date":"2018-03-14T22:35:32","date_gmt":"2018-03-15T03:35:32","guid":{"rendered":"http:\/\/bluegalaxy.info\/codewalk\/?p=1727"},"modified":"2018-03-14T22:35:32","modified_gmt":"2018-03-15T03:35:32","slug":"javascript-use-array-map-method","status":"publish","type":"post","link":"https:\/\/bluegalaxy.info\/codewalk\/2018\/03\/14\/javascript-use-array-map-method\/","title":{"rendered":"JavaScript: How to use the array.map( ) method"},"content":{"rendered":"

The JavaScript map()<\/code>method creates a new array<\/strong> with the results of calling a provided function on every element<\/strong> in this array. For example, lets say you have a small array of numbers called “numbers”:<\/p>\n

var numbers = [1, 4, 9];<\/pre>\n
We can use .map <\/strong>on this array to find the square root of each of the elements in numbers AND assign those results to a new array called ‘roots’:<\/p>\n
var roots = numbers.map(Math.sqrt);<\/pre>\n
\/\/ roots now contains [1, 2, 3], numbers still contains [1, 4, 9]<\/pre>\n
Here is another example of using map()<\/code>from the mozilla JavaScript reference site. This example shows how to use map on a String to get an array of bytes in the ASCII encoding representing the character values:<\/p>\n
var map = Array.prototype.map;\r\nvar a = map.call('Hello World', function(x) { \r\n  return x.charCodeAt(0); \r\n});\r\nconsole.log(a);<\/pre>\n
which yields:<\/p>\n
[72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100]<\/pre>\n
These values can be independently verified with my JavaScript Ascii Engine!<\/p>\n
JavaScript Web App: JavaScript ASCII Engine<\/a><\/p><\/blockquote>\n