CODEWITHSUNDEEP
javascript
meadowstream
meadowstream

Reputation: 4141

Undefined is not a function when calling getTime on new Date

I get "undefined is not a function" when trying to run this. What am I missing?

function bench(func) {
  var start = new Date.getTime();

  for(var i = 0; i < 10000; i++) {
    func();
  }

  console.log(func, new Date.getTime() - start);
}

function forLoop() {

    var counter = 0;
    for(var i = 0; i < 10; i++) {
      counter += 1;
    }

    return counter;

}

bench(forLoop);

Upvotes: 2

Views: 8847

Answers (2)

jfriend00
jfriend00

Reputation: 707456

You need to use:

new Date().getTime();

instead of

new Date.getTime();

Here's some explanation of what was doing on. When you do:

new Date.getTime();

it looks for the getTime() property on the Date constructor and that is undefined because that property exists on the prototype or actual instantiated objects, not on the constructor itself. Then it tries to do new undefined which obviously doesn't work and gives you the error you saw.

When you do:

new Date().getTime();

It is essentially doing this:

(new Date()).getTime();

because of operator precedence and that is what you want. It will create a new Date() object and then call the .getTime() method on it.

Upvotes: 6

Robin Drexler
Robin Drexler

Reputation: 4457

You need to instantiate the Date object before invoking methods on it.

Example:

var date = new Date()
start = date.getTime();

http://jsfiddle.net/3TJLq/

Upvotes: 1

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