Trying to learn how to use classes with javascript, not sure how to initialize class correctly

Question

Not sure why this construction of a class is not working, maybe I'm just calling the function in the wrong way? Here is my code:

  function zeros(bits, pattern) {
    this.bits = bits;
    this.pattern = pattern;
  };

  zeros.prototype.short = function() {
    return this.bits.match(this.pattern)[0].length;
  };

  heyJude = zeros('1100110011001100000011000000111111001100111111001111110000000000000011001111110011111100111111000000110011001111110000001111110011001100000011', /([0]).*?\1+/);
  console.log(heyJude.short());

Worth noting that JavaScript doesn't have classes in the sense that class-based OOP languages like Java and C# do. JavaScript uses prototypical inheritance (an object has a reference to another object which is its prototype, from which it can inherit properties). What you have above is a constructor function (zeros) and associated object (zeros.prototype). You use it with new, which creates a new object backed by the object that zeros.prototype points to, then calls zeros with this referring to that new object. ES2015 adds class, which is primarily just more convenient syntax. — T.J. Crowder
– T.J. Crowder, Commented Feb 5, 2016 at 18:18
Perhaps also worth noting that the overwhelming convention in JavaScript is to name constructor functions with an initial capital letter, e.g. Zeros rather than zeros, whereas other functions are (by convention) named with an initial lower-case letter. — T.J. Crowder
– T.J. Crowder, Commented Feb 5, 2016 at 18:20

T.J. Crowder · Accepted Answer · 2016-02-05 18:14:11Z

6

Call it via the new keyword:

var heyJude = new zeros('...');

edited Feb 5, 2016 at 18:14

T.J. Crowder

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answered Feb 5, 2016 at 18:13

madox2

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Community · Accepted Answer · 2020-06-20 09:12:55Z

3

You need to initialize the object using the new operator

This will instantiate an instance of your zeros class.

var heyJude = new zeros('110.....

Taken from MDN (modified for context):

When the code new zeros(...) is executed, the following things happen:

A new object is created, inheriting from zeros.prototype.

The constructor function zeros is called with the specified arguments and this bound to the newly created object. new zeros is equivalent to new zeros(), i.e. if no argument list is specified, zeros is called without arguments.

The object returned by the constructor function becomes the result of the whole new expression. If the constructor function doesn't explicitly return an object, the object created in step 1 is used instead. (Normally constructors don't return a value, but they can choose to do so if they want to override the normal object creation process.)

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Feb 5, 2016 at 18:14

bluetoft

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2 Comments

T.J. Crowder Over a year ago

When quoting, use blockquotes to avoid the appearance of plagarism.

bluetoft Over a year ago

Thanks again! @T.J.Crowder

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