Benbacardi's code logic

[netwarriorgizmo]

I'm interested in the logic behind a section of code Benbacardi posted in answer to one of my questions some weeks ago. I wonder if anyone would care to explain it so i can understand what's going on? Firstly here is the code:

Code: Select all

age = 0

while (parseInt(age) < 5){
    age = window.prompt('Please enter your age','');
}

if (age >59) {
    document.write ('The price of your ticket is a concessionary £8');
} else {
    document.write ('The price of your ticket is £10');
}

I'm interested in two specifics here. Firstly can anyone explain the differences between using the functions ParsFloat & ParseInt and perhaps provide some examples of where each should be used.

Also, I notoced Benbacardi started off with declaring the variable = 0. This worked well but I though that the only time a variable needed to be initialised was within a for loop. What is the significance of declaring it as = 0 here, in the context of this piece of code rather than simply creating an empty variable which allows the user to input their own value???:

netwarriorgizmo

[Webforumz Staff]

ParseInt tries to convert a value to an integer and parsefloat tries to convert to a float.

like "age5.3" would convert to "5" with parseint, and "5.3" with parsefloat.

The initialization of the variable is because it's being used in the conditional of the while loop. The first time through the while it needs a value that will fail the while comparison so that it asks for the age at least once. A null value and empty aren't the same thing, null stands for value unknown, so comparing things to null doesn't always work the way you think it might.

[netwarriorgizmo]

This is interesting. In the Introduction to JavaScript course I've done ParseFloat is used exclusively to turn numerical information into number representations when ParseInt would be more appropriate. I've learned something here then.

Not too sure I'm grasping the significance of the 0 value though. If this initialises the variable to 0 value I don't understand why the loop doesn't produce the same results (based on a null value) by follwign the if logic??:

netwarriorgizmo