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1. JavaScript Objects > The String, Number, and Boolean Primitive Values Act Li...
The String, Number, and Boolean Primitive Values Act Like Objects When Used Like Objects
When a primitive value is used as if it were an object created by a constructor, JavaScript converts it to an object in order to respond to the expression at hand, but then discards the object qualities and changes it back to a primitive value. In the code below, I take primitive values and showcase what happens when the values are treated like objects.
<!DOCTYPE html><html lang="en"><body><script> // Produce primitive values var myNull = null; var myUndefined = undefined; var primitiveString1 = "foo"; var primitiveString2 = String('foo'); // did not use new, so we get primitive var primitiveNumber1 = 10; var primitiveNumber2 = Number('10'); // did not use new, so we get primitive var primitiveBoolean1 = true; var primitiveBoolean2 = Boolean('true'); // did not use new, so we get primitive /* Access the toString() property method (inherited by objects from object.prototype) to demonstrate that the primitive values are converted to objects when treated like objects. */ // logs "string string" console.log(primitiveString1.toString(), primitiveString2.toString()); // logs "number number" console.log(primitiveNumber1.toString(), primitiveNumber2.toString()); // logs "boolean boolean" console.log(primitiveBoolean1.toString(), primitiveBoolean2.toString()); /* This will throw an error and not show up in firebug lite, as null and undefined do not convert to objects and do not have constructors. */ console.log(myNull.toString()); console.log(myUndefined.toString()); </script></body></html>
