Array#invoke Useful JavaScript Game Extension #24

Array#invoke is a method to make the common task of inoking a method on all elements in an array easier. Though you could use your own anonymous function as a map or each iterator to achieve the same result, this shortcut method makes it clear what the intention is and removes the extra syntax clutter.

What invoke does is to call the named method on each element in the array, passing in any arguments if given.

/**
* Invoke the named method on each element in the array
* and return a new array containing the results of the invocation.
*
* @param {String} method The name of the method to invoke.
* @param [arg...] Optional arguments to pass to the method being invoked.
*
* @type Array
* @returns A new array containing the results of invoking the 
* named method on each element.
*/
Array.prototype.invoke = function(method) {
  var args = Array.prototype.slice.call(arguments, 1);
 
  return this.map(function(element) {
    return element[method].apply(element, args);
  });
};

Here are some examples of it in action:

[1.1, 2.2, 3.3, 4.4].invoke("floor")
=> [1, 2, 3, 4]
 
['hello', 'world', 'cool!'].invoke('substring', 0, 3)
=> ['hel', 'wor', 'coo']

The result of each invocation is returned in an array. This allows for easy chaining of data transformations:

values.invoke("scale", 4).invoke("subtract", 3)...

Fans of Ruby and Rails will know about Symbol#to_proc, a closely related idiom:

names = people.map &:name

Thanks for reading!

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