Quotes About Programming

the truth is JavaScript actually makes two passes over your page: in the first pass it reads all the function definitions, and in the second it begins executing your code. So

So, we recommend specifying the width and height in the tag attributes, and not setting those properties in CSS unless you really mean to scale the canvas.

Yes, workers can access localStorage and make XMLHttpRequests.

If the two values have different types, try to convert them into the same type and then compare them

When you delete a property, you're not just deleting the value of the property, you're deleting the property itself. And, if you try to use fido.dogYears after deleting it, it will evaluate to undefined.

An expression is anything that evaluates to a value. 3+4

Here's the short story: functions are objects in JavaScript. In

in JavaScript just about everything is an object underneath, even

the constructor always has a prototype property. More

Now, when we have an environment that has a value for each of the free variables, we say that we've closed the function. And, when we take the function and the environment together, we say we have a closure.

Take what varies and "encapsulate" it so it won't affect the rest of your code.

A function without a return statement returns undefined.

If a variable is declared outside a function, it's GLOBAL. If it's declared inside a function, it's LOCAL.

when you assign a value to a variable name that hasn't been previously declared, it is treated as a new, global variable. So be careful, if you do this within a function you are creating a global variable. Note

methods in objects are properties too. They just happen to have a function assigned to them.

When you link to multiple JavaScript files from your page, all the global variables are defined in the same global space.

If you assign a new variable without using the var keyword, that variable will be global, even if you are first assigning it in a function.

an important thing to know about JavaScript: there's one queue and one "thread of control," meaning there is only one of me going through the events one at a time.

We haven't done much writing code, but we are reading and understanding code, and that can be just as good. So

In fact, there's a keyword in JavaScript named this, and that is exactly how you tell JavaScript you mean this object we're in.

A callback works like this: give a function to the object that knows about the event. When the event occurs, that object will call you back, or notify you, by calling that function. You're going to see this pattern in JavaScript for a variety of events.

As it turns out, one of the things the new operator does behind the scenes when the object is created is to store information that allows it to determine, at any time, the constructor that created the object. And

When you declare any kind of global variable or define a global function, it is stored as a property in the window object. So

You see, now that we have a prototype, if we add any methods to that prototype, even after we've already created dog objects, all dogs inheriting from the prototype immediately and automatically get this new behavior.