Javascript result is the function as a string not the array element I was expecting

Question

my JavaScript object has an array in it but when I try to return an element of the array I get the function as a string instead of the value of the array element.

My code is

  function Car(make, model){
    this.make = make;
    this.model = model;
    this.dimensions = [4, 3, 1.8];
    this.carLength = function(){ return this.dimensions[0]; };
  }

  var c = new Car("Ford", "Escort");

  alert(c.make);
  alert(c.model);
  alert(c.dimensions[0]);
  alert(c.carLength);

The first 3 alerts show the data expected, ("Ford", "Escort" and 4), the forth one displays the following output

function(){ return this.dimensions[0]; }

Why is the function being listed and not executed?

CarInstance.carLength is a method. You have to call it, or you'll just get the function. console.log(c.carLength()) — StackSlave
– StackSlave, Commented Sep 1, 2020 at 0:45
Because this is a function, to execute use () at the end. Example: alert(c.carLength()) — Aks Jacoves
– Aks Jacoves, Commented Sep 1, 2020 at 0:45

Nathan Mc Grath · Accepted Answer · 2020-09-01 00:47:00Z

1

You need to include parentheses to execute the function.

alert(c.carLength());

If you don't include the parentheses, then you are just passing a reference to the function into the alert function as a variable. Then alert will execute toString() on that variable.

When you include the parentheses, you are passing the value that is returned from executing the function.

answered Sep 1, 2020 at 0:47

Nathan Mc Grath

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